Maxamps 11,1V 8000 mAh on RCM CRT.5 extended chassis?

[GO-RIDE.com]

I'm currently using 4800 lipo car packs, so there is no room for the esc on the chassis. I mount the esc on the RCM radio plate the and radio on the center diff plate. This works, but I think it leaves the car too top heavy. I'm getting some the the Maxamps 100mm length batts next week. I just can decide between 3100 3S, 4200 2S, and 4200 3S.

If I go 3S I need to get a MM / Feigao combo and new pinions. If I stay 2S then I just need the batts. The problem I have is my CRT.5 drains a 4800 2S pretty fast on the indoor clay track I drive. I'm currently running a GTB / 6.5 setup. Its fast and doesn't get hot, but I'm wondering if higher voltage will run longer?