[RC-Monster Mike]

I have a pair of Polyquest 4s 3100mah packs, that together weigh around the same as 8-9 cells. These, wired in parallel and using a mild motor like the Lehner basic xl2800 on a light truck (9 pounds +/-) would perform very well(fast enough to spank the Novak system) and have a nice, long runtime).
The 5000mah 6s pack is not something I have, but merely a suggestion that would provide excellent speed, power and runtime. For extended runtime, cooling measure are a necessity for most systems.