I am now using an ACE stock with a 11.1V 1200mAH Firefox 3-cell LiPo battery. Fits like a dream. Although some dremmelling was required to run the wires from the rear of the receiver in through the "buffer tube" of the stock.

Here is a pic of the ACE Stock :
http://www.coldwarshooters.net/image...on%20Stock.jpg

I'm almost done this custom gun project, so I'll post some pics (tonight) in the Airsoft Media section of ASC here, and on my site (www.6mm-mag.com).