diff --git a/src/include/xpr/vpos_type.cc.h b/src/include/xpr/vpos_type.cc.h
index 69f6461..19ebb9a 100644
--- a/src/include/xpr/vpos_type.cc.h
+++ b/src/include/xpr/vpos_type.cc.h
@@ -7,28 +7,6 @@
 
 namespace CNORXZ
 {
-    /****************
-     *   VPosBase   *
-     ****************/
-    /*
-    template <SizeT N>
-    inline Uptr<VPosBase> VPosBase::vextend(const SPos<N>& a) const
-    {
-	return this->vextend(UPos(N));
-    }
-
-    template <SizeT N, SizeT... Ms>
-    inline Uptr<VPosBase> VPosBase::vextend(const SFPos<N,Ms...>& a) const
-    {
-	return this->vextend(static_cast<FPos>(a));
-    }
-
-    template <class PosT1, class PosT2>
-    inline Uptr<VPosBase> VPosBase::vextend(const MPos<PosT1,PosT2>& a) const
-    {
-	return this->vextend(static_cast<const PosT1&>(a))->vextend(a.next());
-    }
-    */
     /************
      *   VPos   *
      ************/
@@ -88,35 +66,7 @@ namespace CNORXZ
 	typedef decltype((*this)(UPos(a->vval()))) OPosT;
 	return std::make_unique<VPos<OPosT>>( (*this)(UPos(a->vval())) );
     }
-    /*
-    template <class PosT>
-    Uptr<VPosBase> VPos<PosT>::vextend(const UPos& a) const
-    {
-	typedef decltype(this->extend(a)) OPosT;
-	return std::make_unique<VPos<OPosT>>(this->extend(a));
-    } 
 
-    template <class PosT>
-    Uptr<VPosBase> VPos<PosT>::vextend(const FPos& a) const
-    {
-	typedef decltype(this->extend(a)) OPosT;
-	return std::make_unique<VPos<OPosT>>(this->extend(a));
-    }
-
-    template <class PosT>
-    Uptr<VPosBase> VPos<PosT>::vextend(const DPos& a) const
-    {
-	typedef decltype(this->extend(a)) OPosT;
-	return std::make_unique<VPos<OPosT>>(this->extend(a));
-    }
-
-    template <class PosT>
-    Uptr<VPosBase> VPos<PosT>::vextend(const DPosRef& a) const
-    {
-	typedef decltype(this->extend(DPos(a))) OPosT;
-	return std::make_unique<VPos<OPosT>>(this->extend(DPos(a)));
-    }
-    */
     /******************
      *   VPos<MPos>   *
      ******************/
@@ -190,8 +140,8 @@ namespace CNORXZ
     template <class PosT1, class PosT2>
     Uptr<VPosBase> VPos<MPos<PosT1,PosT2>>::vplus(const VPosBase* a) const
     {
-	typedef decltype((*this) + DPosRef(a)) OPosT;
-	return std::make_unique<VPos<OPosT>>((*this) + DPosRef(a));
+	typedef decltype((*this) + PosFromVPos<MPos<PosT1,PosT2>>::make(a)) OPosT;
+	return std::make_unique<VPos<OPosT>>((*this) + PosFromVPos<MPos<PosT1,PosT2>>::make(a));
     }
     
     template <class PosT1, class PosT2>
@@ -207,35 +157,7 @@ namespace CNORXZ
 	typedef decltype( (*this)(UPos(a->vval())) ) OPosT;
 	return std::make_unique<VPos<OPosT>>( (*this)(UPos(a->vval())) );
     }
-    /*
-    template <class PosT1, class PosT2>
-    Uptr<VPosBase> VPos<MPos<PosT1,PosT2>>::vextend(const UPos& a) const 
-    {
-	typedef decltype(this->extend(DPos(a))) OPosT;
-	return std::make_unique<VPos<OPosT>>(this->extend(DPos(a)));
-    }
-    
-    template <class PosT1, class PosT2>
-    Uptr<VPosBase> VPos<MPos<PosT1,PosT2>>::vextend(const FPos& a) const 
-    {
-	typedef decltype(this->extend(DPos(a))) OPosT;
-	return std::make_unique<VPos<OPosT>>(this->extend(DPos(a)));
-    }
 
-    template <class PosT1, class PosT2>
-    Uptr<VPosBase> VPos<MPos<PosT1,PosT2>>::vextend(const DPos& a) const
-    {
-	typedef decltype(this->extend(a)) OPosT;
-	return std::make_unique<VPos<OPosT>>(this->extend(a));
-    }
-    
-    template <class PosT1, class PosT2>
-    Uptr<VPosBase> VPos<MPos<PosT1,PosT2>>::vextend(const DPosRef& a) const
-    {
-	typedef decltype(this->extend(DPos(a))) OPosT;
-	return std::make_unique<VPos<OPosT>>(this->extend(DPos(a)));
-    }
-    */
     /***************
      *   VPosRef   *
      ***************/
@@ -295,35 +217,7 @@ namespace CNORXZ
 	typedef decltype( (*mC)(UPos(a->vval())) ) OPosT;
 	return std::make_unique<VPos<OPosT>>( (*mC)(UPos(a->vval())) );
     }
-    /*
-    template <class PosT>
-    Uptr<VPosBase> VPosRef<PosT>::vextend(const UPos& a) const 
-    {
-	typedef decltype(mC->extend(a)) OPosT;
-	return std::make_unique<VPos<OPosT>>(mC->extend(a));
-    }
-    
-    template <class PosT>
-    Uptr<VPosBase> VPosRef<PosT>::vextend(const FPos& a) const 
-    {
-	typedef decltype(mC->extend(a)) OPosT;
-	return std::make_unique<VPos<OPosT>>(mC->extend(a));
-    }
 
-    template <class PosT>
-    Uptr<VPosBase> VPosRef<PosT>::vextend(const DPos& a) const
-    {
-	typedef decltype(mC->extend(a)) OPosT;
-	return std::make_unique<VPos<OPosT>>(mC->extend(a));
-    }
-
-    template <class PosT>
-    Uptr<VPosBase> VPosRef<PosT>::vextend(const DPosRef& a) const
-    {
-	typedef decltype(mC->extend(DPos(a))) OPosT;
-	return std::make_unique<VPos<OPosT>>(mC->extend(DPos(a)));
-    }
-    */
     /*********************
      *   VPosRef<MPos>   *
      *********************/
@@ -376,8 +270,8 @@ namespace CNORXZ
     template <class PosT1, class PosT2>
     Uptr<VPosBase> VPosRef<MPos<PosT1,PosT2>>::vplus(const VPosBase* a) const
     {
-	typedef decltype((*mC) + DPosRef(a)) OPosT;
-	return std::make_unique<VPos<OPosT>>((*mC) + DPosRef(a));
+	typedef decltype((*mC) + PosFromVPos<MPos<PosT1,PosT2>>::make(a)) OPosT;
+	return std::make_unique<VPos<OPosT>>((*mC) + PosFromVPos<MPos<PosT1,PosT2>>::make(a));
     }
     
     template <class PosT1, class PosT2>
@@ -393,35 +287,25 @@ namespace CNORXZ
 	typedef decltype( (*mC)(UPos(a->vval())) ) OPosT;
 	return std::make_unique<VPos<OPosT>>( (*mC)(UPos(a->vval())) );
     }
-    /*
-    template <class PosT1, class PosT2>
-    Uptr<VPosBase> VPosRef<MPos<PosT1,PosT2>>::vextend(const UPos& a) const
-    {
-	typedef decltype(mC->extend(DPos(a))) OPosT;
-	return std::make_unique<VPos<OPosT>>(mC->extend(DPos(a)));
-    }
-
-    template <class PosT1, class PosT2>
-    Uptr<VPosBase> VPosRef<MPos<PosT1,PosT2>>::vextend(const FPos& a) const
-    {
-	typedef decltype(mC->extend(DPos(a))) OPosT;
-	return std::make_unique<VPos<OPosT>>(mC->extend(DPos(a)));
-    }
-
-    template <class PosT1, class PosT2>
-    Uptr<VPosBase> VPosRef<MPos<PosT1,PosT2>>::vextend(const DPos& a) const
-    {
-	typedef decltype(mC->extend(a)) OPosT;
-	return std::make_unique<VPos<OPosT>>(mC->extend(a));
-    }
     
-    template <class PosT1, class PosT2>
-    Uptr<VPosBase> VPosRef<MPos<PosT1,PosT2>>::vextend(const DPosRef& a) const
+    /*******************
+     *   PosFromVPos   *
+     *******************/
+
+    template <class PosT>
+    inline decltype(auto) PosFromVPos<PosT>::make(const VPosBase* a)
     {
-	typedef decltype(mC->extend(DPos(a))) OPosT;
-	return std::make_unique<VPos<OPosT>>(mC->extend(DPos(a)));
+	return PosT(a->vval());
+    }
+
+    template <class PosT1, class PosT2>
+    inline decltype(auto) PosFromVPos<MPos<PosT1,PosT2>>::make(const VPosBase* a)
+    {
+#if CXZ_DEBUG
+	CXZ_ASSERT(a->vnext() != nullptr, "VPos does not match required size");
+#endif
+	return MPos<PosT1,PosT2>(a->vval(), PosFromVPos<PosT2>::make(a->vnext()));
     }
-    */
 }
 
 #endif
diff --git a/src/include/xpr/vpos_type.h b/src/include/xpr/vpos_type.h
index f2f85ec..fd86d2e 100644
--- a/src/include/xpr/vpos_type.h
+++ b/src/include/xpr/vpos_type.h
@@ -4,8 +4,6 @@
 
 #include "base/base.h"
 
-#define MAX_VMPOS_DEPTH 4
-
 namespace CNORXZ
 {
     class VPosBase
@@ -21,20 +19,6 @@ namespace CNORXZ
 	virtual Uptr<VPosBase> vplus(const VPosBase* a) const = 0;
 	virtual Uptr<VPosBase> vtimes(const VPosBase* a) const = 0;
 	virtual Uptr<VPosBase> vexec(const VPosBase* a) const = 0;
-	//virtual Uptr<VPosBase> vextend(const UPos& a) const = 0;
-	//virtual Uptr<VPosBase> vextend(const FPos& a) const = 0;
-	//virtual Uptr<VPosBase> vextend(const DPos& a) const = 0;
-	//virtual Uptr<VPosBase> vextend(const DPosRef& a) const = 0;
-	/*
-	template <SizeT N>
-	inline Uptr<VPosBase> vextend(const SPos<N>& a) const;
-
-	template <SizeT N, SizeT... Ms>
-	inline Uptr<VPosBase> vextend(const SFPos<N,Ms...>& a) const;
-
-	template <class PosT1, class PosT2>
-	inline Uptr<VPosBase> vextend(const MPos<PosT1,PosT2>& a) const;
-	*/
     };
 
     template <class PosT>
@@ -53,10 +37,6 @@ namespace CNORXZ
 	virtual Uptr<VPosBase> vplus(const VPosBase* a) const override final;
 	virtual Uptr<VPosBase> vtimes(const VPosBase* a) const override final;
 	virtual Uptr<VPosBase> vexec(const VPosBase* a) const override final;
-	//virtual Uptr<VPosBase> vextend(const UPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const FPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const DPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const DPosRef& a) const override final;
     };
 
     template <class PosT1, class PosT2>
@@ -81,10 +61,6 @@ namespace CNORXZ
 	virtual Uptr<VPosBase> vplus(const VPosBase* a) const override final;
 	virtual Uptr<VPosBase> vtimes(const VPosBase* a) const override final;
 	virtual Uptr<VPosBase> vexec(const VPosBase* a) const override final;
-	//virtual Uptr<VPosBase> vextend(const UPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const FPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const DPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const DPosRef& a) const override final;
     };
 
     template <class PosT>
@@ -105,10 +81,6 @@ namespace CNORXZ
 	virtual Uptr<VPosBase> vplus(const VPosBase* a) const override final;
 	virtual Uptr<VPosBase> vtimes(const VPosBase* a) const override final;
 	virtual Uptr<VPosBase> vexec(const VPosBase* a) const override final;
-	//virtual Uptr<VPosBase> vextend(const UPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const FPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const DPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const DPosRef& a) const override final;
 
     };
 
@@ -133,10 +105,6 @@ namespace CNORXZ
 	virtual Uptr<VPosBase> vplus(const VPosBase* a) const override final;
 	virtual Uptr<VPosBase> vtimes(const VPosBase* a) const override final;
 	virtual Uptr<VPosBase> vexec(const VPosBase* a) const override final;
-	//virtual Uptr<VPosBase> vextend(const UPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const FPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const DPos& a) const override final;
-	//virtual Uptr<VPosBase> vextend(const DPosRef& a) const override final;
     };
 
     
@@ -180,6 +148,17 @@ namespace CNORXZ
     class VPosRef<DPosRef>
     {};
 
+    template <class PosT>
+    struct PosFromVPos
+    {
+	static inline decltype(auto) make(const VPosBase* a);
+    };
+
+    template <class PosT1, class PosT2>
+    struct PosFromVPos<MPos<PosT1,PosT2>>
+    {
+	static inline decltype(auto) make(const VPosBase* a);
+    };
 
 }
 
diff --git a/src/tests/xpr_unit_test.cc b/src/tests/xpr_unit_test.cc
index 30f67b2..bb2280d 100644
--- a/src/tests/xpr_unit_test.cc
+++ b/src/tests/xpr_unit_test.cc
@@ -157,38 +157,6 @@ namespace
 	EXPECT_EQ(dp5.sub().val(), mS4p.val() * mUp1.val());
     }
 
-    TEST_F(Pos_Test, DynExtend)
-    {/*
-	DPos dp1(mkMPos(static_cast<UPos>(mS2p), mUp1));
-	DPos dp2(mkMPos(mUp2, static_cast<UPos>(mS4p)));
-	auto dp3 = dp1.extend(mUp2);
-	auto dp4 = dp2.extend(mS2p);
-	auto dp5 = dp3 + dp4;
-	DPos dp01(mUp1);
-	auto dp6 = dp3 * dp01;
-
-	EXPECT_EQ( dp3.size(), 3u );
-	EXPECT_EQ( dp4.size(), 3u );
-
-	EXPECT_EQ( dp3.val(), mS2p.val() );
-	EXPECT_EQ( dp3.next().val(), mUp1.val() );
-	EXPECT_EQ( dp3.next().next().val(), mUp2.val() );
-
-    	EXPECT_EQ( dp4.val(), mUp2.val() );
-	EXPECT_EQ( dp4.next().val(), mS4p.val() );
-	EXPECT_EQ( dp4.next().next().val(), mS2p.val() );
-
-	EXPECT_EQ( dp5.size(), 3u );
-	EXPECT_EQ( dp6.size(), 3u );
-
-	EXPECT_EQ( dp5.val(), dp3.val() + dp4.val() );
-	EXPECT_EQ( dp5.next().val(), dp3.next().val() + dp4.next().val() );
-	EXPECT_EQ( dp5.next().next().val(), dp3.next().next().val() + dp4.next().next().val() );
-
-	EXPECT_EQ( dp6.val(), dp3.val() * dp01.val() );
-	EXPECT_EQ( dp6.next().val(), dp3.next().val() * dp01.val() );
-	EXPECT_EQ( dp6.next().next().val(), dp3.next().next().val() * dp01.val() );
-     */}
 }
 
 int main(int argc, char** argv)