I just got my Vltor stock in last week and I see some have modified the caps to fit 3 CR123 batteries by shaving some plastic off.Mine look impossible to modify because with 3 batteries in the tube,the battery sicks out about 1/8" and would require me to cut about 1/4" off both caps and I don't think they'd lock into place.This has to be one of the most piss-poor designs I've ever seen.What the hell were these guys thinking?

Relax,

There are longer battery compartments coming soon that will fit the CAR length stocks and fit 3 123s in each tube.  Its easy to punch holes in a previous design, its harder to engineer, ground up, a product and "fore-see" holes.  I believe, the original thinking, was to leave the ability to use the sling slots accessible to the shooter.  I believe, though, many are expressing they are less interested in the sling slots, w/ the increasing use of receiver end plate sling mts, and KAC's push button swivels.  
BTW, Eric over at Vltor, heard our rquests and got right on it.  My 2.

S2

I asked the same thing....

Rumor has it that trimming the caps will work, but no one has actually posted pictures.  Rumor also has it Vltor is working on longer tubes that will fit 3.  Right now it's 2 123's and a piece of foam per side.