Ive been having the same problem!
I wanted the UV coordinates (either pixels or 1 to 0) but the trace function doesn't seem to return the correct values.

I would really appreciate a solution. I am planning on creating a small code to handle bullet fire as actual holes (tranparent) in some entities such as crates to make my games and simulations more realistic.

Sorry for writing in english, I translated your German but I can't write it.

-Mike-

http://www.groundtacticsgame.com/
Alienware m17x R Custom laptop
specs:
Intel Core 2 Extreme Quad CPU Q9300
2x Nvidia 280GTX 2GB vram
6GB ddr3 memory@ 1333Mhz
512GB SSD
1200p 17' screen
runs Crysis Warhead on max settings at 1200p at 90 fps