Thanks!

OK one final dumb question. I assume that the vertex structure in the A6 engine is hard-wired into A6 code via a DrawindexPrimitive or somesuch, hence:

v0 - always contains the position
v3 - always contains the normal
v7 - always contains a texture1 coordinate
v8 - always contains a texture2 coordinate

what are the missing registers used for? Typical MS associations are:
blendweight, blendindices,psize,pdiffuse,specular,tangent,binormal etc. However I don't see how to either find these, or if possible, alter them.