Lua as a Data File: minor setback

I'm having to rethink my approach a bit--if I expose a struct, say a Vertex, to Lua that has something like an XMFLOAT* or D3DXVECTOR* member, I get an access violation when I try to instantiate one from Lua. Took me a bit to realize that was the issue. I'm not sure I can make it work without going to plain old float members. I guess I can write a function on the C++ side that handles mesh creation based on a Lua table, but I was really hoping to be able to do it all in the script.