Battery/ROF question

Okay, so I've fixed my ICS sig 552. It's working great, except for the fact that the battery compartment won't fit conventional batteries. I found this peq box. What do ya'll think? Good by or no? Also, it turns out that the guy I bought the gun from put in a double toothed gear, which is rather annoying. My ROF is waaayyy too high, and I'm afraid I'll get excessive jamming with that 11.1 lipo. Any suggestions. I want the peq and the lipo, but I need a lower ROF. I'd like to just put in a normal gear, but I'm not sure what to look for. I'm not even sure which is the double toothed one yet. I may buy an altogether new gearbox. I would appreciate input.