the projection of the back and right side is overlapping with the front and left side which sometimes makes sense but it just was a quickly done example... in my opinion there seldom will be the same amount of vertices in both maps and that's what i wanted to point out!

how would a new mesh get generated? (that's what i meant all the time in my above posts with having to do "a complete mesh loader" instead of only having to add the second uvs to the already existing vertices!)

i guess this would also involve generating a new index buffer?

...
at least i wasn't talking total nonsense - i just didn't explain it in a good enough way.