I think I have a problem like that with one of my... ermm... project models. How many faces does it have and more importantly are they all concentrated in one area, because I think that's what's happening with my model.
Mine is rounded, so there are plenty of poly's in a high concentration, and I'm sure I've seen some shots pass through it... but it might just be my bad shooting.
If you do have a high concentration of Poly's, all I can think of is try to get rid of as many as you can and spread them out a bit more...
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"Supernova, ya supernova, supernova goes pop
supernova, ya think it's over but the supernova don't stop" PM5K
Death:"Arnold Judas Rimmer... your life is over. You will travel with me to the-"
#knees death in the groin#
Rimmer:"Remember matey, it's only the good that die young"
Kudoth, god of pointless educational programs.