Rendering wise, the surface/mesh system is also likely to change a bit. B3d surfaces actually contain a 'hidden' internal mesh (b3d 'meshes' are really a container 'meshmodel' for multiple surfaces) and I want to make this side of things public.
So, that might explain why I couldn't build meshes that were compatible with a stencil shadow system! ARGH!!! All this time and I couldn't figure it out. Making a closed mesh in Blitz3D is almost impossible :( Maybe I'm not skilled enough.