Reading this again is sparking some renewed interest in running tracer again for indoor game play.
However, I have seen someone modify their tracer unit by chopping the can in half; effectively separating the battery compartment and the photo strobe unit, then running the batteries to a PEQ-style box.
This is something I would definitely want to try, as the only reason I wouldn't run tracer indoors is the extra length in front of my rifle that I wouldn't want manipulating my rifle in CQB.
Anybody know who has done this? I can't recall who it was at Siege that I saw that had this done on their tracer unit. He was running it on a pistol too.