diff --git a/Grid/serialisation/BaseIO.h b/Grid/serialisation/BaseIO.h
index 4d9bd9e0..043762ea 100644
--- a/Grid/serialisation/BaseIO.h
+++ b/Grid/serialisation/BaseIO.h
@@ -36,41 +36,41 @@ Author: Guido Cossu <guido.cossu@ed.ac.uk>
 #include <Grid/Eigen/unsupported/CXX11/Tensor>
 
 namespace Grid {
-  // TODO Support Grid::complex from GPU port
-  //template<typename T> using Grid_complex = std::complex<T>;
-
-  // Returns original type, except for Grid_complex, where it returns the underlying type
-  //template<typename T> struct RealType { using type = T; };
-  //template<typename T> struct RealType<Grid_complex<T>> { using type = T; };
-
   namespace EigenIO {
-    //template<typename T> struct is_complex : public std::false_type {};
-    //template<typename T> struct is_complex<Grid_complex<T>>
-        //: std::integral_constant<bool, std::is_arithmetic<T>::value> {};
+    // EigenIO works for scalars that are not just Grid supported scalars
+    template<typename T, typename V = void> struct is_complex : public std::false_type {};
+    // Support all complex types (not just Grid complex types) - even if the definitions overlap (!)
+    template<typename T> struct is_complex<             T , typename
+        std::enable_if< ::Grid::is_complex<             T >::value>::type> : public std::true_type {};
+    template<typename T> struct is_complex<std::complex<T>, typename
+        std::enable_if<!::Grid::is_complex<std::complex<T>>::value>::type> : public std::true_type {};
 
-    // Eigen tensors can be composed of arithmetic scalar and complex types
-    template<typename T> struct is_scalar : std::integral_constant<bool,
-                            std::is_arithmetic<T>::value || is_complex<T>::value> {};
-
-    // Eigen tensors can also be composed of a limited number of containers
-    // NB: grid tensors (iScalar, iVector, iMatrix) have stricter limits on complex types
-    //template <typename T> struct is_container                       : public std::false_type {};
-    //template <typename T> struct is_container<iScalar<T>>           : public std::true_type {};
-    //template <typename T, int N> struct is_container<iVector<T, N>> : public std::true_type {};
-    //template <typename T, int N> struct is_container<iMatrix<T, N>> : public std::true_type {};
-    //template <typename T, std::size_t N> struct is_container<std::array<T, N>> : public std::true_type {};
+    // Helpers to support I/O for Eigen tensors of arithmetic scalars, complex types, or Grid tensors
+    template<typename T, typename V = void> struct is_scalar : public std::false_type {};
+    template<typename T> struct is_scalar<T, typename std::enable_if<std::is_arithmetic<T>::value || is_complex<T>::value>::type> : public std::true_type {};
 
     // Is this an Eigen tensor
     template<typename T> struct is_tensor : std::integral_constant<bool,
       std::is_base_of<Eigen::TensorBase<T, Eigen::ReadOnlyAccessors>, T>::value> {};
 
     // Is this an Eigen tensor of a supported scalar
-    template<typename T, typename C = void> struct is_tensor_of_scalar : public std::false_type {};
-    template<typename T> struct is_tensor_of_scalar<T, typename std::enable_if<is_tensor<T>::value && is_scalar<typename T::Scalar>::value, void>::type> : public std::true_type {};
+    template<typename T, typename V = void> struct is_tensor_of_scalar : public std::false_type {};
+    template<typename T> struct is_tensor_of_scalar<T, typename std::enable_if<is_tensor<T>::value && is_scalar<typename T::Scalar>::value>::type> : public std::true_type {};
 
     // Is this an Eigen tensor of a supported container
-    template<typename T, typename C = void> struct is_tensor_of_container : public std::false_type {};
-    template<typename T> struct is_tensor_of_container<T, typename std::enable_if<is_tensor<T>::value && isGridTensor<typename T::Scalar>::value, void>::type> : public std::true_type {};
+    template<typename T, typename V = void> struct is_tensor_of_container : public std::false_type {};
+    template<typename T> struct is_tensor_of_container<T, typename std::enable_if<is_tensor<T>::value && isGridTensor<typename T::Scalar>::value>::type> : public std::true_type {};
+
+    // Traits are the default for scalars, or come from GridTypeMapper for GridTensors
+    template<typename T, typename V = void> struct Traits {};
+    template<typename T> struct Traits<T, typename std::enable_if<is_tensor_of_scalar<T>::value>::type> : public GridTypeMapper_Base {
+      using scalar_type = typename T::Scalar;
+      static constexpr bool is_complex = ::Grid::EigenIO::is_complex<scalar_type>::value;
+    };
+    template<typename T> struct Traits<T, typename std::enable_if<is_tensor_of_container<T>::value>::type> : public GridTypeMapper<typename T::Scalar> {
+      using scalar_type = typename GridTypeMapper<typename T::Scalar>::scalar_type;
+      static constexpr bool is_complex = ::Grid::EigenIO::is_complex<scalar_type>::value;
+    };
 
     // Is this a fixed-size Eigen tensor
     template<typename T> struct is_tensor_fixed : public std::false_type {};
@@ -84,83 +84,9 @@ namespace Grid {
         : public std::true_type {};
 
     // Is this a variable-size Eigen tensor
-    template<typename T, typename C = void> struct is_tensor_variable : public std::false_type {};
+    template<typename T, typename V = void> struct is_tensor_variable : public std::false_type {};
     template<typename T> struct is_tensor_variable<T, typename std::enable_if<is_tensor<T>::value
-        && !is_tensor_fixed<T>::value, void>::type> : public std::true_type {};
-
-    // These traits describe the Eigen tensor scalar and container objects supported for IO
-    // Containers are arbitrarily deeply nested compositions of fixed size objects,
-    // ... grid tensors (iScalar, iVector, and iMatrix) and std::array
-    // EigenIO::Traits are not defined for Eigen tensors, but rather their top-level scalar
-    // This is because Eigen tensors have a dynamic size flavour, but the scalars are all fixed size
-    // This allows the traits to all be defined as constexpr
-    /*template <typename T, typename C = void> struct Traits {}; // C needed for specialisation
-    // This defines the bottom level - i.e. it's a description of the underlying scalar
-    template <typename T> struct Traits<T, typename std::enable_if<is_scalar<T>::value, void>::type> {
-      using scalar_type = T; // Type of the underlying scalar
-      using scalar_real = typename RealPart<scalar_type>::type; // real type underlying scalar_type
-      static constexpr unsigned int rank = 0;   // The rank of the grid tensor (i.e. how many indices used)
-      //static constexpr unsigned int rank_non_trivial = 0; // As per rank, but excludes those of dimension 1
-      static constexpr unsigned int count = 1;  // total number of elements (i.e. product of dimensions)
-      static constexpr std::size_t scalar_size = sizeof(T);    // Size of the underlying scalar in bytes
-      static constexpr std::size_t size = scalar_size * count; // total size of elements in bytes
-      static constexpr std::size_t Dimension(unsigned int dim) { return 0; } // Dimension size
-      //static constexpr std::size_t DimensionNT(unsigned int dim) { return 0; } // non-trivial dim size
-      // e.g. iScalar<iVector<Complex,1>>
-      //      rank  = 2
-      //      rank_non_trivial = 0
-      //      count  = 1
-      // e.g. iVector<iMatrix<Complex,3>,1>
-      //      rank  = 3
-      //      rank_non_trivial = 2
-      //      count  = 9
-      // e.g. iScalar<iVector<iMatrix<Complex,3>,4>>
-      //      rank  = 4
-      //      rank_non_trivial = 3
-      //      count  = 36
-    };
-    template <typename T> struct Traits<iScalar<T>> {
-      using scalar_type = typename Traits<T>::scalar_type;
-      using scalar_real = typename RealPart<scalar_type>::type;
-      static constexpr unsigned int rank = 1 + Traits<T>::rank;
-      //static constexpr unsigned int rank_non_trivial = 0 + Traits<T>::rank_non_trivial;
-      static constexpr unsigned int count = 1 * Traits<T>::count;
-      static constexpr std::size_t scalar_size = Traits<T>::scalar_size;
-      static constexpr std::size_t size = scalar_size * count;
-      static constexpr std::size_t Dimension(unsigned int dim) {
-        return ( dim == 0 ) ? 1 : Traits<T>::Dimension(dim - 1); }
-      //static constexpr std::size_t DimensionNT(unsigned int dim) {
-        //return Traits<T>::DimensionNT(dim); }
-    };
-    template <typename T, int N> struct Traits<iVector<T, N>> {
-      using scalar_type = typename Traits<T>::scalar_type;
-      using scalar_real = typename RealPart<scalar_type>::type;
-      static constexpr unsigned int rank = 1 + Traits<T>::rank;
-      //static constexpr unsigned int rank_non_trivial = (N>1 ? 1 : 0) + Traits<T>::rank_non_trivial;
-      static constexpr unsigned int count = N * Traits<T>::count;
-      static constexpr std::size_t scalar_size = Traits<T>::scalar_size;
-      static constexpr std::size_t size = scalar_size * count;
-      static constexpr std::size_t Dimension(unsigned int dim) {
-        return ( dim == 0 ) ? N : Traits<T>::Dimension(dim - 1); }
-      //static constexpr std::size_t DimensionNT(unsigned int dim) {
-        //return ( N == 1 ) ? Traits<T>::DimensionNT(dim) : ( dim == 0 ) ? N : Traits<T>::DimensionNT(dim - 1);
-      //}
-    };
-    template <typename T, int N> struct Traits<iMatrix<T, N>> {
-      using scalar_type = typename Traits<T>::scalar_type;
-      using scalar_real = typename RealPart<scalar_type>::type;
-      static constexpr unsigned int rank = 2 + Traits<T>::rank;
-      //static constexpr unsigned int rank_non_trivial = (N>1 ? 2 : 0) + Traits<T>::rank_non_trivial;
-      static constexpr unsigned int count = N * N * Traits<T>::count;
-      static constexpr std::size_t scalar_size = Traits<T>::scalar_size;
-      static constexpr std::size_t size = scalar_size * count;
-      static constexpr std::size_t Dimension(unsigned int dim) {
-        return ( dim == 0 || dim == 1 ) ? N : Traits<T>::Dimension(dim - 2); }
-      //static constexpr std::size_t DimensionNT(unsigned int dim) {
-        //return ( N == 1 ) ? Traits<T>::DimensionNT(dim) : ( dim == 0 || dim == 1 ) ? N : Traits<T>::DimensionNT(dim - 2);
-      //}
-    };
-    template <typename T, int N> struct Traits<std::array<T, N>> : Traits<iVector<T, N>> {};*/
+        && !is_tensor_fixed<T>::value>::type> : public std::true_type {};
   }
 
   // Abstract writer/reader classes ////////////////////////////////////////////
@@ -177,11 +103,10 @@ namespace Grid {
     void push(const std::string &s);
     void pop(void);
     template <typename U>
-    typename std::enable_if<std::is_base_of<Serializable, U>::value, void>::type
+    typename std::enable_if<std::is_base_of<Serializable, U>::value>::type
     write(const std::string& s, const U &output);
     template <typename U>
-    typename std::enable_if<!std::is_base_of<Serializable, U>::value
-                         && !EigenIO::is_tensor<U>::value, void>::type
+    typename std::enable_if<!std::is_base_of<Serializable, U>::value && !EigenIO::is_tensor<U>::value>::type
     write(const std::string& s, const U &output);
     template <typename U>
     void write(const std::string &s, const iScalar<U> &output);
@@ -190,19 +115,21 @@ namespace Grid {
     template <typename U, int N>
     void write(const std::string &s, const iMatrix<U, N> &output);
     template <typename ETensor>
-    typename std::enable_if<EigenIO::is_tensor<ETensor>::value, void>::type
+    typename std::enable_if<EigenIO::is_tensor<ETensor>::value>::type
     write(const std::string &s, const ETensor &output);
 
     // Helper functions for Scalar vs Container specialisations
     template <typename ETensor>
-    inline typename std::enable_if<EigenIO::is_tensor_of_scalar<ETensor>::value, const typename GridTypeMapper<typename ETensor::Scalar>::scalar_type *>::type
+    inline typename std::enable_if<EigenIO::is_tensor_of_scalar<ETensor>::value,
+    const typename ETensor::Scalar *>::type
     getFirstScalar(const ETensor &output)
     {
       return output.data();
     }
     
     template <typename ETensor>
-    inline typename std::enable_if<EigenIO::is_tensor_of_container<ETensor>::value, const typename GridTypeMapper<typename ETensor::Scalar>::scalar_type *>::type
+    inline typename std::enable_if<EigenIO::is_tensor_of_container<ETensor>::value,
+    const typename EigenIO::Traits<ETensor>::scalar_type *>::type
     getFirstScalar(const ETensor &output)
     {
       return output.data()->begin();
@@ -210,7 +137,7 @@ namespace Grid {
     
     template <typename S>
     inline typename std::enable_if<EigenIO::is_scalar<S>::value, void>::type
-    copyScalars(typename GridTypeMapper<S>::scalar_type * &pCopy, const S &Source)
+    copyScalars(S * &pCopy, const S &Source)
     {
       * pCopy ++ = Source;
     }
@@ -268,7 +195,7 @@ namespace Grid {
     // Helper functions for Scalar vs Container specialisations
     template <typename S>
     inline typename std::enable_if<EigenIO::is_scalar<S>::value, void>::type
-    copyScalars(S &Dest, const typename GridTypeMapper<S>::scalar_type * &pSource)
+    copyScalars(S &Dest, const S * &pSource)
     {
       Dest = * pSource ++;
     }
@@ -362,7 +289,7 @@ namespace Grid {
   {
     using Index = typename ETensor::Index;
     using Container = typename ETensor::Scalar; // NB: could be same as scalar
-    using Traits = GridTypeMapper<Container>;
+    using Traits = EigenIO::Traits<ETensor>;
     using Scalar = typename Traits::scalar_type; // type of the underlying scalar
     constexpr unsigned int TensorRank{ETensor::NumIndices};
     constexpr unsigned int ContainerRank{Traits::Rank}; // Only non-zero for containers
@@ -386,10 +313,6 @@ namespace Grid {
     Scalar * pCopyBuffer = nullptr;
     const Index TotalNumElements = NumElements * Traits::count;
     if( !CopyData ) {
-      /*if constexpr ( ContainerRank == 0 )
-        pWriteBuffer = output.data();
-      else
-        pWriteBuffer = output.data()->begin();*/
       pWriteBuffer = getFirstScalar( output );
     } else {
       // Regardless of the Eigen::Tensor storage order, the copy will be Row Major
@@ -400,12 +323,6 @@ namespace Grid {
       for( auto &idx : MyIndex ) idx = 0;
       for( auto n = 0; n < NumElements; n++ ) {
         const Container & c = output( MyIndex );
-        /*if constexpr ( ContainerRank == 0 )
-          * pCopy ++ = c;
-        else {
-          for( const Scalar &Source : c )
-            * pCopy ++ = Source;
-        }*/
         copyScalars( pCopy, c );
         // Now increment the index
         for( int i = output.NumDimensions - 1; i >= 0 && ++MyIndex[i] == output.dimension(i); i-- )
@@ -513,7 +430,7 @@ namespace Grid {
   {
     using Index = typename ETensor::Index;
     using Container = typename ETensor::Scalar; // NB: could be same as scalar
-    using Traits = GridTypeMapper<Container>;
+    using Traits = EigenIO::Traits<ETensor>;
     using Scalar = typename Traits::scalar_type; // type of the underlying scalar
     constexpr unsigned int TensorRank{ETensor::NumIndices};
     constexpr unsigned int ContainerRank{Traits::Rank}; // Only non-zero for containers
diff --git a/Grid/simd/Grid_vector_types.h b/Grid/simd/Grid_vector_types.h
index b34e056d..707af211 100644
--- a/Grid/simd/Grid_vector_types.h
+++ b/Grid/simd/Grid_vector_types.h
@@ -10,6 +10,7 @@ Author: Azusa Yamaguchi <ayamaguc@staffmail.ed.ac.uk>
 Author: Guido Cossu <cossu@iroiro-pc.kek.jp>
 Author: Peter Boyle <paboyle@ph.ed.ac.uk>
 Author: neo <cossu@post.kek.jp>
+Author: Michael Marshall <michael.marshall@ed.ac.au>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -865,8 +866,10 @@ template <typename T>
 struct is_simd : public std::false_type {};
 template <> struct is_simd<vRealF>     : public std::true_type {};
 template <> struct is_simd<vRealD>     : public std::true_type {};
+template <> struct is_simd<vRealH>     : public std::true_type {};
 template <> struct is_simd<vComplexF>  : public std::true_type {};
 template <> struct is_simd<vComplexD>  : public std::true_type {};
+template <> struct is_simd<vComplexH>  : public std::true_type {};
 template <> struct is_simd<vInteger>   : public std::true_type {};
 
 template <typename T> using IfSimd    = Invoke<std::enable_if<is_simd<T>::value, int> >;
diff --git a/Grid/tensors/Tensor_class.h b/Grid/tensors/Tensor_class.h
index c87503c6..d59640df 100644
--- a/Grid/tensors/Tensor_class.h
+++ b/Grid/tensors/Tensor_class.h
@@ -5,6 +5,7 @@ Copyright (C) 2015
 
 Author: Azusa Yamaguchi <ayamaguc@staffmail.ed.ac.uk>
 Author: Peter Boyle <paboyle@ph.ed.ac.uk>
+Author: Michael Marshall <michael.marshall@ed.ac.au>
 
 This program is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
@@ -42,27 +43,26 @@ namespace Grid {
 //
 class GridTensorBase {};
 
+// Too late to remove these traits from Grid Tensors, so inherit from GridTypeMapper
+#define GridVector_CopyTraits \
+  using element = vtype; \
+  using scalar_type     = typename Traits::scalar_type; \
+  using vector_type     = typename Traits::vector_type; \
+  using vector_typeD    = typename Traits::vector_typeD; \
+  using tensor_reduced  = typename Traits::tensor_reduced; \
+  using scalar_object   = typename Traits::scalar_object; \
+  using Complexified    = typename Traits::Complexified; \
+  using Realified       = typename Traits::Realified; \
+  using DoublePrecision = typename Traits::DoublePrecision; \
+  static constexpr int TensorLevel = Traits::TensorLevel
+
 template <class vtype>
 class iScalar {
  public:
   vtype _internal;
 
-  typedef vtype element;
-  typedef typename GridTypeMapper<vtype>::scalar_type scalar_type;
-  typedef typename GridTypeMapper<vtype>::vector_type vector_type;
-  typedef typename GridTypeMapper<vtype>::vector_typeD vector_typeD;
-  typedef typename GridTypeMapper<vtype>::tensor_reduced tensor_reduced_v;
-  typedef typename GridTypeMapper<vtype>::scalar_object recurse_scalar_object;
-  typedef iScalar<tensor_reduced_v> tensor_reduced;
-  typedef iScalar<recurse_scalar_object> scalar_object;
-  // substitutes a real or complex version with same tensor structure
-  typedef iScalar<typename GridTypeMapper<vtype>::Complexified> Complexified;
-  typedef iScalar<typename GridTypeMapper<vtype>::Realified> Realified;
-
-  // get double precision version
-  typedef iScalar<typename GridTypeMapper<vtype>::DoublePrecision> DoublePrecision;
-  
-  static constexpr int TensorLevel = GridTypeMapper<vtype>::TensorLevel + 1;
+  using Traits = GridTypeMapper<iScalar<vtype> >;
+  GridVector_CopyTraits;
 
   // Scalar no action
   //  template<int Level> using tensor_reduce_level = typename
@@ -173,37 +173,10 @@ class iScalar {
     return stream;
   };
 
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline begin() const { return &_internal; }
-
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline begin() const { return _internal.begin(); }
-
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline end() const { return (&_internal) + 1; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline end() const { return _internal.begin() + sizeof(_internal)/sizeof(scalar_type); }
-
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, scalar_type *>::type
-  strong_inline begin() { return &_internal; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, scalar_type *>::type
-  strong_inline begin() { return _internal.begin(); }
-  
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, scalar_type *>::type
-  strong_inline end() { return (&_internal) + 1; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, scalar_type *>::type
-  strong_inline end() { return _internal.begin() + sizeof(_internal)/sizeof(scalar_type); }
+  strong_inline const scalar_type * begin() const { return reinterpret_cast<const scalar_type *>(&_internal); }
+  strong_inline       scalar_type * begin()       { return reinterpret_cast<      scalar_type *>(&_internal); }
+  strong_inline const scalar_type * end()   const { return begin() + Traits::count; }
+  strong_inline       scalar_type * end()         { return begin() + Traits::count; }
 };
 ///////////////////////////////////////////////////////////
 // Allows to turn scalar<scalar<scalar<double>>>> back to double.
@@ -224,22 +197,9 @@ class iVector {
  public:
   vtype _internal[N];
 
-  typedef vtype element;
-  typedef typename GridTypeMapper<vtype>::scalar_type scalar_type;
-  typedef typename GridTypeMapper<vtype>::vector_type vector_type;
-  typedef typename GridTypeMapper<vtype>::vector_typeD vector_typeD;
-  typedef typename GridTypeMapper<vtype>::tensor_reduced tensor_reduced_v;
-  typedef typename GridTypeMapper<vtype>::scalar_object recurse_scalar_object;
-  typedef iScalar<tensor_reduced_v> tensor_reduced;
-  typedef iVector<recurse_scalar_object, N> scalar_object;
+  using Traits = GridTypeMapper<iVector<vtype, N> >;
+  GridVector_CopyTraits;
 
-  // substitutes a real or complex version with same tensor structure
-  typedef iVector<typename GridTypeMapper<vtype>::Complexified, N> Complexified;
-  typedef iVector<typename GridTypeMapper<vtype>::Realified, N> Realified;
-
-  // get double precision version
-  typedef iVector<typename GridTypeMapper<vtype>::DoublePrecision, N> DoublePrecision;
-  
   template <class T, typename std::enable_if<!isGridTensor<T>::value, T>::type
                          * = nullptr>
   strong_inline auto operator=(T arg) -> iVector<vtype, N> {
@@ -248,7 +208,6 @@ class iVector {
     return *this;
   }
 
-  static constexpr int TensorLevel = GridTypeMapper<vtype>::TensorLevel + 1;
   iVector(const Zero &z) { *this = zero; };
   iVector() = default;
   /*
@@ -334,37 +293,10 @@ class iVector {
   //      return _internal[i];
   //    }
 
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline begin() const { return _internal; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline begin() const { return _internal[0].begin(); }
-  
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline end() const { return _internal + N; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline end() const { return _internal[0].begin() + sizeof(_internal)/sizeof(scalar_type); }
-
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, scalar_type *>::type
-  strong_inline begin() { return _internal; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, scalar_type *>::type
-  strong_inline begin() { return _internal[0].begin(); }
-  
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, scalar_type *>::type
-  strong_inline end() { return _internal + N; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, scalar_type *>::type
-  strong_inline end() { return _internal[0].begin() + sizeof(_internal)/sizeof(scalar_type); }
+  strong_inline const scalar_type * begin() const { return reinterpret_cast<const scalar_type *>(_internal); }
+  strong_inline       scalar_type * begin()       { return reinterpret_cast<      scalar_type *>(_internal); }
+  strong_inline const scalar_type * end()   const { return begin() + Traits::count; }
+  strong_inline       scalar_type * end()         { return begin() + Traits::count; }
 };
 
 template <class vtype, int N>
@@ -372,25 +304,8 @@ class iMatrix {
  public:
   vtype _internal[N][N];
 
-  typedef vtype element;
-  typedef typename GridTypeMapper<vtype>::scalar_type scalar_type;
-  typedef typename GridTypeMapper<vtype>::vector_type vector_type;
-  typedef typename GridTypeMapper<vtype>::vector_typeD vector_typeD;
-  typedef typename GridTypeMapper<vtype>::tensor_reduced tensor_reduced_v;
-  typedef typename GridTypeMapper<vtype>::scalar_object recurse_scalar_object;
-
-  // substitutes a real or complex version with same tensor structure
-  typedef iMatrix<typename GridTypeMapper<vtype>::Complexified, N> Complexified;
-  typedef iMatrix<typename GridTypeMapper<vtype>::Realified, N> Realified;
-
-  // get double precision version
-  typedef iMatrix<typename GridTypeMapper<vtype>::DoublePrecision, N> DoublePrecision;
-  
-  // Tensor removal
-  typedef iScalar<tensor_reduced_v> tensor_reduced;
-  typedef iMatrix<recurse_scalar_object, N> scalar_object;
-
-  static constexpr int TensorLevel = GridTypeMapper<vtype>::TensorLevel + 1;
+  using Traits = GridTypeMapper<iMatrix<vtype, N> >;
+  GridVector_CopyTraits;
 
   iMatrix(const Zero &z) { *this = zero; };
   iMatrix() = default;
@@ -521,37 +436,10 @@ class iMatrix {
   //    return _internal[i][j];
   //  }
 
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline begin() const { return _internal[0]; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline begin() const { return _internal[0][0].begin(); }
-  
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline end() const { return _internal[0] + N * N; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, const scalar_type *>::type
-  strong_inline end() const { return _internal[0][0].begin() + sizeof(_internal)/sizeof(scalar_type); }
-
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, scalar_type *>::type
-  strong_inline begin() { return _internal[0]; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, scalar_type *>::type
-  strong_inline begin() { return _internal[0][0].begin(); }
-  
-  template <typename T = vtype>
-  typename std::enable_if<!isGridTensor<T>::value, scalar_type *>::type
-  strong_inline end() { return _internal[0] + N * N; }
-  
-  template <typename T = vtype>
-  typename std::enable_if<isGridTensor<T>::value, scalar_type *>::type
-  strong_inline end() { return _internal[0][0].begin() + sizeof(_internal)/sizeof(scalar_type); }
+  strong_inline const scalar_type * begin() const { return reinterpret_cast<const scalar_type *>(_internal[0]); }
+  strong_inline       scalar_type * begin()       { return reinterpret_cast<      scalar_type *>(_internal[0]); }
+  strong_inline const scalar_type * end()   const { return begin() + Traits::count; }
+  strong_inline       scalar_type * end()         { return begin() + Traits::count; }
 };
 
 template <class v>
@@ -574,6 +462,3 @@ void vprefetch(const iMatrix<v, N> &vv) {
 }
 }
 #endif
-
-
-
diff --git a/Grid/tensors/Tensor_traits.h b/Grid/tensors/Tensor_traits.h
index d4854768..9cb93e17 100644
--- a/Grid/tensors/Tensor_traits.h
+++ b/Grid/tensors/Tensor_traits.h
@@ -5,6 +5,7 @@
 Author: Azusa Yamaguchi <ayamaguc@staffmail.ed.ac.uk>
 Author: Peter Boyle <paboyle@ph.ed.ac.uk>
 Author: Christopher Kelly <ckelly@phys.columbia.edu>
+Author: Michael Marshall <michael.marshall@ed.ac.au>
     This program is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
     the Free Software Foundation; either version 2 of the License, or
@@ -32,14 +33,10 @@ namespace Grid {
   template<class T, int N> class iMatrix;
 
   // These are the Grid tensors
-  template<typename T> struct isGridTensor
-  : public std::false_type { static constexpr bool notvalue = true; };
-  template<class T> struct isGridTensor<iScalar<T>>
-  : public std::true_type { static constexpr bool notvalue = false; };
-  template<class T, int N> struct isGridTensor<iVector<T, N>>
-  : public std::true_type { static constexpr bool notvalue = false; };
-  template<class T, int N> struct isGridTensor<iMatrix<T, N>>
-  : public std::true_type { static constexpr bool notvalue = false; };
+  template<typename T>     struct isGridTensor                : public std::false_type { static constexpr bool notvalue = true; };
+  template<class T>        struct isGridTensor<iScalar<T>>    : public std::true_type  { static constexpr bool notvalue = false; };
+  template<class T, int N> struct isGridTensor<iVector<T, N>> : public std::true_type  { static constexpr bool notvalue = false; };
+  template<class T, int N> struct isGridTensor<iMatrix<T, N>> : public std::true_type  { static constexpr bool notvalue = false; };
 
 //////////////////////////////////////////////////////////////////////////////////
 // Want to recurse: GridTypeMapper<Matrix<vComplexD> >::scalar_type == ComplexD.
@@ -57,20 +54,15 @@ namespace Grid {
 //////////////////////////////////////////////////////////////////////////////////
 
   // This saves repeating common properties for supported Grid Scalar types
-  template<typename T, typename V=void> struct GridTypeMapper_Base {};
   // TensorLevel    How many nested grid tensors
   // Rank           Rank of the grid tensor
   // count          Total number of elements, i.e. product of dimensions
-  // scalar_size    Size of the underlying fundamental object (tensor_reduced) in bytes
-  // size           Total size of all elements in bytes
   // Dimension(dim) Size of dimension dim
-  template<typename T> struct GridTypeMapper_Base<T> {
+  struct GridTypeMapper_Base {
     static constexpr int TensorLevel = 0;
     static constexpr int Rank = 0;
     static constexpr std::size_t count = 1;
-    static constexpr std::size_t scalar_size = sizeof(T);
-    static constexpr std::size_t size = scalar_size * count;
-    static constexpr int Dimension(unsigned int dim) { return 0; }
+    static constexpr int Dimension(int dim) { return 0; }
   };
 
 //////////////////////////////////////////////////////////////////////////////////
@@ -79,7 +71,7 @@ namespace Grid {
 
   template<typename T> struct GridTypeMapper {};
 
-  template<> struct GridTypeMapper<RealF> : public GridTypeMapper_Base<RealF> {
+  template<> struct GridTypeMapper<RealF> : public GridTypeMapper_Base {
     typedef RealF scalar_type;
     typedef RealF vector_type;
     typedef RealD vector_typeD;
@@ -89,7 +81,7 @@ namespace Grid {
     typedef RealF Realified;
     typedef RealD DoublePrecision;
   };
-  template<> struct GridTypeMapper<RealD> : public GridTypeMapper_Base<RealD> {
+  template<> struct GridTypeMapper<RealD> : public GridTypeMapper_Base {
     typedef RealD scalar_type;
     typedef RealD vector_type;
     typedef RealD vector_typeD;
@@ -99,7 +91,7 @@ namespace Grid {
     typedef RealD Realified;
     typedef RealD DoublePrecision;
   };
-  template<> struct GridTypeMapper<ComplexF> : public GridTypeMapper_Base<ComplexF> {
+  template<> struct GridTypeMapper<ComplexF> : public GridTypeMapper_Base {
     typedef ComplexF scalar_type;
     typedef ComplexF vector_type;
     typedef ComplexD vector_typeD;
@@ -109,7 +101,7 @@ namespace Grid {
     typedef RealF Realified;
     typedef ComplexD DoublePrecision;
   };
-  template<> struct GridTypeMapper<ComplexD> : public GridTypeMapper_Base<ComplexD> {
+  template<> struct GridTypeMapper<ComplexD> : public GridTypeMapper_Base {
     typedef ComplexD scalar_type;
     typedef ComplexD vector_type;
     typedef ComplexD vector_typeD;
@@ -119,7 +111,7 @@ namespace Grid {
     typedef RealD Realified;
     typedef ComplexD DoublePrecision;
   };
-  template<> struct GridTypeMapper<Integer> : public GridTypeMapper_Base<Integer> {
+  template<> struct GridTypeMapper<Integer> : public GridTypeMapper_Base {
     typedef Integer scalar_type;
     typedef Integer vector_type;
     typedef Integer vector_typeD;
@@ -130,7 +122,7 @@ namespace Grid {
     typedef void DoublePrecision;
   };
 
-  template<> struct GridTypeMapper<vRealF> : public GridTypeMapper_Base<vRealF> {
+  template<> struct GridTypeMapper<vRealF> : public GridTypeMapper_Base {
     typedef RealF  scalar_type;
     typedef vRealF vector_type;
     typedef vRealD vector_typeD;
@@ -140,7 +132,7 @@ namespace Grid {
     typedef vRealF Realified;
     typedef vRealD DoublePrecision;
   };
-  template<> struct GridTypeMapper<vRealD> : public GridTypeMapper_Base<vRealD> {
+  template<> struct GridTypeMapper<vRealD> : public GridTypeMapper_Base {
     typedef RealD  scalar_type;
     typedef vRealD vector_type;
     typedef vRealD vector_typeD;
@@ -150,7 +142,17 @@ namespace Grid {
     typedef vRealD Realified;
     typedef vRealD DoublePrecision;
   };
-  template<> struct GridTypeMapper<vComplexH> : public GridTypeMapper_Base<vComplexH> {
+  template<> struct GridTypeMapper<vRealH> : public GridTypeMapper_Base {
+    typedef RealF  scalar_type;
+    typedef vRealH vector_type;
+    typedef vRealD vector_typeD;
+    typedef vRealH tensor_reduced;
+    typedef RealF  scalar_object;
+    typedef vComplexH Complexified;
+    typedef vRealH Realified;
+    typedef vRealD DoublePrecision;
+  };
+  template<> struct GridTypeMapper<vComplexH> : public GridTypeMapper_Base {
     typedef ComplexF  scalar_type;
     typedef vComplexH vector_type;
     typedef vComplexD vector_typeD;
@@ -160,7 +162,7 @@ namespace Grid {
     typedef vRealH Realified;
     typedef vComplexD DoublePrecision;
   };
-  template<> struct GridTypeMapper<vComplexF> : public GridTypeMapper_Base<vComplexF> {
+  template<> struct GridTypeMapper<vComplexF> : public GridTypeMapper_Base {
     typedef ComplexF  scalar_type;
     typedef vComplexF vector_type;
     typedef vComplexD vector_typeD;
@@ -170,7 +172,7 @@ namespace Grid {
     typedef vRealF Realified;
     typedef vComplexD DoublePrecision;
   };
-  template<> struct GridTypeMapper<vComplexD> : public GridTypeMapper_Base<vComplexD> {
+  template<> struct GridTypeMapper<vComplexD> : public GridTypeMapper_Base {
     typedef ComplexD  scalar_type;
     typedef vComplexD vector_type;
     typedef vComplexD vector_typeD;
@@ -180,7 +182,7 @@ namespace Grid {
     typedef vRealD Realified;
     typedef vComplexD DoublePrecision;
   };
-  template<> struct GridTypeMapper<vInteger> : public GridTypeMapper_Base<vInteger> {
+  template<> struct GridTypeMapper<vInteger> : public GridTypeMapper_Base {
     typedef  Integer scalar_type;
     typedef vInteger vector_type;
     typedef vInteger vector_typeD;
@@ -192,46 +194,49 @@ namespace Grid {
   };
 
 #define GridTypeMapper_RepeatedTypes \
-  typedef typename ObjectTraits::scalar_type scalar_type; \
-  typedef typename ObjectTraits::vector_type vector_type; \
-  typedef typename ObjectTraits::vector_typeD vector_typeD; \
-  typedef typename ObjectTraits::tensor_reduced tensor_reduced; \
-  typedef typename ObjectTraits::scalar_object scalar_object; \
-  typedef typename ObjectTraits::Complexified Complexified; \
-  typedef typename ObjectTraits::Realified Realified; \
-  typedef typename ObjectTraits::DoublePrecision DoublePrecision; \
-  static constexpr int TensorLevel = BaseTraits::TensorLevel + 1; \
-  static constexpr std::size_t scalar_size = BaseTraits::scalar_size; \
-  static constexpr std::size_t size = scalar_size * count
+  using BaseTraits   = GridTypeMapper<T>; \
+  using scalar_type  = typename BaseTraits::scalar_type; \
+  using vector_type  = typename BaseTraits::vector_type; \
+  using vector_typeD = typename BaseTraits::vector_typeD; \
+  static constexpr int TensorLevel = BaseTraits::TensorLevel + 1
 
   template<typename T> struct GridTypeMapper<iScalar<T>> {
-    using ObjectTraits = iScalar<T>;
-    using BaseTraits = GridTypeMapper<T>;
-    static constexpr int Rank = 1 + BaseTraits::Rank;
-    static constexpr std::size_t count = 1 * BaseTraits::count;
-    static constexpr int Dimension(unsigned int dim) {
-      return ( dim == 0 ) ? 1 : BaseTraits::Dimension(dim - 1); }
     GridTypeMapper_RepeatedTypes;
+    using tensor_reduced  = iScalar<typename BaseTraits::tensor_reduced>;
+    using scalar_object   = iScalar<typename BaseTraits::scalar_object>;
+    using Complexified    = iScalar<typename BaseTraits::Complexified>;
+    using Realified       = iScalar<typename BaseTraits::Realified>;
+    using DoublePrecision = iScalar<typename BaseTraits::DoublePrecision>;
+    static constexpr int Rank = BaseTraits::Rank + 1;
+    static constexpr std::size_t count = BaseTraits::count;
+    static constexpr int Dimension(int dim) {
+      return ( dim == 0 ) ? 1 : BaseTraits::Dimension(dim - 1); }
   };
 
   template<typename T, int N> struct GridTypeMapper<iVector<T, N>> {
-    using ObjectTraits = iVector<T, N>;
-    using BaseTraits = GridTypeMapper<T>;
-    static constexpr int Rank = 1 + BaseTraits::Rank;
-    static constexpr std::size_t count = N * BaseTraits::count;
-    static constexpr int Dimension(unsigned int dim) {
-      return ( dim == 0 ) ? N : BaseTraits::Dimension(dim - 1); }
     GridTypeMapper_RepeatedTypes;
+    using tensor_reduced  = iScalar<typename BaseTraits::tensor_reduced>;
+    using scalar_object   = iVector<typename BaseTraits::scalar_object,   N>;
+    using Complexified    = iVector<typename BaseTraits::Complexified,    N>;
+    using Realified       = iVector<typename BaseTraits::Realified,       N>;
+    using DoublePrecision = iVector<typename BaseTraits::DoublePrecision, N>;
+    static constexpr int Rank = BaseTraits::Rank + 1;
+    static constexpr std::size_t count = BaseTraits::count * N;
+    static constexpr int Dimension(int dim) {
+      return ( dim == 0 ) ? N : BaseTraits::Dimension(dim - 1); }
   };
 
   template<typename T, int N> struct GridTypeMapper<iMatrix<T, N>> {
-    using ObjectTraits = iMatrix<T, N>;
-    using BaseTraits = GridTypeMapper<T>;
-    static constexpr int Rank = 2 + BaseTraits::Rank;
-    static constexpr std::size_t count = N * N * BaseTraits::count;
-    static constexpr int Dimension(unsigned int dim) {
-      return ( dim == 0 || dim == 1 ) ? N : BaseTraits::Dimension(dim - 2); }
     GridTypeMapper_RepeatedTypes;
+    using tensor_reduced  = iScalar<typename BaseTraits::tensor_reduced>;
+    using scalar_object   = iMatrix<typename BaseTraits::scalar_object,   N>;
+    using Complexified    = iMatrix<typename BaseTraits::Complexified,    N>;
+    using Realified       = iMatrix<typename BaseTraits::Realified,       N>;
+    using DoublePrecision = iMatrix<typename BaseTraits::DoublePrecision, N>;
+    static constexpr int Rank = BaseTraits::Rank + 2;
+    static constexpr std::size_t count = BaseTraits::count * N * N;
+    static constexpr int Dimension(int dim) {
+      return ( dim == 0 || dim == 1 ) ? N : BaseTraits::Dimension(dim - 2); }
   };
 
   // Match the index
diff --git a/Grid/util/Eigen.h b/Grid/util/Eigen.h
index 7f5fa915..9af510fe 100644
--- a/Grid/util/Eigen.h
+++ b/Grid/util/Eigen.h
@@ -35,7 +35,7 @@ namespace Grid {
   template <typename ETensor, typename Lambda>
   typename std::enable_if<EigenIO::is_tensor_of_scalar<ETensor>::value, void>::type
   for_all_do_lambda( Lambda lambda, typename ETensor::Scalar &scalar, typename ETensor::Index &Seq,
-                    std::array<std::size_t, ETensor::NumIndices + GridTypeMapper<typename ETensor::Scalar>::Rank> &MyIndex)
+                    std::array<std::size_t, ETensor::NumIndices + EigenIO::Traits<ETensor>::Rank> &MyIndex)
   {
     lambda( scalar, Seq++, MyIndex );
   }
@@ -44,9 +44,9 @@ namespace Grid {
   template <typename ETensor, typename Lambda>
   typename std::enable_if<EigenIO::is_tensor_of_container<ETensor>::value, void>::type
   for_all_do_lambda( Lambda lambda, typename ETensor::Scalar &container, typename ETensor::Index &Seq,
-                    std::array<std::size_t, ETensor::NumIndices + GridTypeMapper<typename ETensor::Scalar>::Rank> &MyIndex)
+                    std::array<std::size_t, ETensor::NumIndices + EigenIO::Traits<ETensor>::Rank> &MyIndex)
   {
-    using Traits = GridTypeMapper<typename ETensor::Scalar>;
+    using Traits = EigenIO::Traits<ETensor>;
     const auto rank{ETensor::NumIndices};
     const auto InnerRank = Traits::Rank;
     for( typename Traits::scalar_type &Source : container ) {
@@ -65,11 +65,12 @@ namespace Grid {
   for_all( ETensor &ET, Lambda lambda )
   {
     using Scalar = typename ETensor::Scalar; // This could be a Container - we'll check later
+    using Traits = EigenIO::Traits<ETensor>;
     const std::size_t NumScalars = ET.size();
     assert( NumScalars > 0 );
     using Index = typename ETensor::Index;
     Index ScalarElementCount{1};
-    const auto InnerRank = GridTypeMapper<Scalar>::Rank;
+    const auto InnerRank = Traits::Rank;
     const auto rank{ETensor::NumIndices};
     std::array<std::size_t, rank + InnerRank> Dims;
     for(auto i = 0; i < rank; i++ ) {
@@ -84,14 +85,13 @@ namespace Grid {
     // If the Scalar is actually a container, add the inner Scalar's dimensions
     size_t InnerScalarCount{1};
     for(auto i = 0; i < InnerRank; i++ ) {
-      auto dim = GridTypeMapper<Scalar>::Dimension(i);
+      auto dim = Traits::Dimension(i);
       assert( dim > 0 );
       Dims[rank + i] = static_cast<std::size_t>(dim);
       assert( Dims[rank + i] == dim ); // check we didn't lose anything in the conversion
       InnerScalarCount *= dim;
     }
-    assert(GridTypeMapper<Scalar>::count == InnerScalarCount);
-    assert(GridTypeMapper<Scalar>::size  == sizeof( Scalar ));
+    assert(Traits::count == InnerScalarCount);
     std::array<std::size_t, rank + InnerRank> MyIndex;
     for( auto &idx : MyIndex ) idx = 0;
     Index Seq = 0;
@@ -119,11 +119,10 @@ namespace Grid {
   // Sequential initialisation of tensors
   // Would have preferred to define template variables for this, but that's c++ 17
   template <typename ETensor>
-  typename std::enable_if<EigenIO::is_tensor<ETensor>::value && !is_complex<typename GridTypeMapper<typename ETensor::Scalar>::scalar_type>::value, void>::type
-  SequentialInit( ETensor &ET, typename GridTypeMapper<typename ETensor::Scalar>::scalar_type Inc = 1,
-                 unsigned short Precision = 0 )
+  typename std::enable_if<EigenIO::is_tensor<ETensor>::value && !EigenIO::Traits<ETensor>::is_complex>::type
+  SequentialInit( ETensor &ET, typename EigenIO::Traits<ETensor>::scalar_type Inc = 1, unsigned short Precision = 0 )
   {
-    using Traits = GridTypeMapper<typename ETensor::Scalar>;
+    using Traits = EigenIO::Traits<ETensor>;
     using scalar_type = typename Traits::scalar_type;
     for_all( ET, [&](scalar_type &c, typename ETensor::Index n, const std::array<size_t, ETensor::NumIndices + Traits::Rank> &Dims ) {
       scalar_type x = Inc * static_cast<scalar_type>(n);
@@ -137,11 +136,10 @@ namespace Grid {
   }
   
   template <typename ETensor>
-  typename std::enable_if<EigenIO::is_tensor<ETensor>::value && is_complex<typename GridTypeMapper<typename ETensor::Scalar>::scalar_type>::value, void>::type
-  SequentialInit( ETensor &ET, typename GridTypeMapper<typename ETensor::Scalar>::scalar_type Inc={1,-1},
-                 unsigned short Precision = 0 )
+  typename std::enable_if<EigenIO::is_tensor<ETensor>::value && EigenIO::Traits<ETensor>::is_complex>::type
+  SequentialInit( ETensor &ET, typename EigenIO::Traits<ETensor>::scalar_type Inc={1,-1}, unsigned short Precision = 0 )
   {
-    using Traits = GridTypeMapper<typename ETensor::Scalar>;
+    using Traits = EigenIO::Traits<ETensor>;
     using scalar_type = typename Traits::scalar_type;
     for_all( ET, [&](scalar_type &c, typename ETensor::Index n, const std::array<size_t, ETensor::NumIndices + Traits::Rank> &Dims ) {
       auto re = Inc.real();
@@ -167,7 +165,7 @@ namespace Grid {
   typename std::enable_if<EigenIO::is_tensor<T>::value, void>::type
   dump_tensor_func(T &t, const char * pName = nullptr)
   {
-    using Traits = GridTypeMapper<typename T::Scalar>;
+    using Traits = EigenIO::Traits<T>;
     const auto rank{T::NumIndices};
     const auto &dims = t.dimensions();
     std::cout << "Dumping rank " << rank << ((T::Options & Eigen::RowMajor) ? ", row" : ", column") << "-major tensor ";
diff --git a/tests/IO/Test_serialisation.cc b/tests/IO/Test_serialisation.cc
index 2ba16361..56cdcb4b 100644
--- a/tests/IO/Test_serialisation.cc
+++ b/tests/IO/Test_serialisation.cc
@@ -110,8 +110,8 @@ void ioTest(const std::string &filename, const O &object, const std::string &nam
 }
 
 typedef ComplexD TestScalar;
-typedef Eigen::TensorFixedSize<Integer, Eigen::Sizes<5,4,3,2,1>> TensorRank5UShort;
-typedef Eigen::TensorFixedSize<Integer, Eigen::Sizes<5,4,3,2,1>, Eigen::StorageOptions::RowMajor> TensorRank5UShortAlt;
+typedef Eigen::TensorFixedSize<unsigned short, Eigen::Sizes<5,4,3,2,1>> TensorRank5UShort;
+typedef Eigen::TensorFixedSize<unsigned short, Eigen::Sizes<5,4,3,2,1>, Eigen::StorageOptions::RowMajor> TensorRank5UShortAlt;
 typedef Eigen::Tensor<TestScalar, 3, Eigen::StorageOptions::RowMajor> TensorRank3;
 typedef Eigen::TensorFixedSize<TestScalar, Eigen::Sizes<9,4,2>, Eigen::StorageOptions::RowMajor> Tensor_9_4_2;
 typedef std::vector<Tensor_9_4_2> aTensor_9_4_2;
@@ -157,11 +157,11 @@ public:
 #define TEST_PARAMS( T ) #T, Flag, Precision, filename, pszExtension, TestNum
 
 template <typename WTR_, typename RDR_, typename T, typename... IndexTypes>
-void EigenTensorTestSingle(const char * MyTypeName, typename GridTypeMapper<typename T::Scalar>::scalar_type Flag,
+void EigenTensorTestSingle(const char * MyTypeName, typename EigenIO::Traits<T>::scalar_type Flag,
                            unsigned short Precision, std::string &filename, const char * pszExtension, unsigned int &TestNum,
                            IndexTypes... otherDims)
 {
-  using Traits = GridTypeMapper<typename T::Scalar>;
+  using Traits = EigenIO::Traits<T>;
   using scalar_type = typename Traits::scalar_type;
   std::unique_ptr<T> pTensor{new T(otherDims...)};
   SequentialInit( * pTensor, Flag, Precision );