Ok, of course. I'd suggest you could write a little app that is loading both X files and then integrates both in one mesh, on 2 texture layers. As long as the triangles and vertices are the same, there shoudn't be a problem. Although, I remember somebody said the vertices will be reindexed sporadicly, and the surface indexing is a also some kind of random game, this would probably require to identify all corresponding triangles by comparing their vertices. But it's possible, just some work to do.