I couldn't run a 7 cell. I only raced in the stock class so 6 cells was the limit. I didn't own a 7 cell anyways. Power was so limited on those stock motors and with the loamy tracks you used up lots of power throwing dirt everywhere. My pinion was ultimately chosen around what would allow me to finish the race before the battery dumped. Having a lighter car made the odds of finishing the race higher. It accelerated a little faster too. Our track wasn't very large and it had some pretty tight curves. The tall spikes on the tires easily dug into the dirt in the corners. We had more problems with understeer than oversteer and traction rolling was an unknown in offroad back then.