Sweet!
Even though the 12 cell might spin the wheels as fast, the lipo will be waaaaay better and have better runtimes...
Depending on how you gear it, you might want to consider a heatsink for the motor...
Basically run it for 20 minutes, then feel it, if its blazing hot consider a heatsink.
And if you eventually burn out the motor PM me and I can give you some recommendations on some 4200 motors that are better and cheaper.
Also you can adjust the starting power through the mamba, this can help alot with the wheelies, and also will help the drivetrain from wearing out too fast...
Anyways, give another report sometime and tell us how your doing with this.