I had a 7XL in my buggy running on 4S. It ran very well, but the motor did get hot on extended runs. I switched to an 8XL and kept the same gearing and the temps got better. The electric buggies are beasts on the track. The power available at the flick of the throttle is unbelieveable.

On the downside, it's like metalman says, tires don't last long. Crimefighters don't last long as it is, but with the electric, they wear out even faster. Of course, my driving style might have something to do with it. I'm not very good, so I tend to take it really easy and then take advantage of the torque to get over the jumps rather than having a rolling start like most do with nitro engines.

I am also finding that I don't need nearly as much top speed as I initially thought I would. At this point, I'm really considering setting my buggy and truggy up for about 30 mph for the track. We run a tight "driver's" track. I'm considering going with a 9XL to keep things cooler.