[lincpimp]

The 7xl is gearing sensitive. I would go with the 12 cell setup and the smaller pinion and give it a try. Get a temp gun and check temps frequently on the first run. If the motor goes over 160 you need to get some more airflow over it and possibly gear down. The rcm heatsink clamp is a good idea if you have a smooth can motor, it will not fit a finned can. Airflow is important with these motors, as they are ineffecient and create a bit of heat regardless of the gearing. I have run a few successful setups with a 7xl, so it can be done.