Unfortunately I have to put the clipping work on hold until the end of the week as I'm heading home for a few days to see my family. In the meantime, I've answered a few of your comments about clipping on the previous post.
Also, here are a few amusing 'outtakes' as I was trying to get the VFPU TnL code working:
Hmm, something wrong with the indexing I think
Something is definitely wrong with the transform matrix (or else Lakitu is drunk :)
M.C. Escher would be proud