apparently you can fix the sorting errors of individual polygons on a model by creating them in the right order. since they aren't sorted, they are just rendered in the order in which they are saved to the file (if that makes sense). so, polygons created last will always appear ontop, and those created first will always appear underneath. i guess it could be possible to create the whole model as normal, and then cut-paste polygons that need to be re-sorted. this could be tedious, but most of the time you would be doing them in groups. i don't actually know if this will work, but i don't see why not.

julz