im not sure how your cells are layed out.. 7 sxs? or a 6cell stick with one on top?
my trucks got two 5s1p 5000mah True-RC packs wired in parallel.
http://www.rc-monster.com/forum/showthread.php?t=6529

the packs are 34mm x 50mm x 160mm, and just barely fit. if your packs are smaller than that, you shouldn't have any problem w/ a similar layout.