I am running the HV 6,5 system on my G-maxx and it suits me fine. Plenty of torque, and an ok top speed. I ahven´t had any problems at all with my system.
I have upgraded almost everything though, in order to make it as solid possible.
You can check it out here:
http://www.rcgalleri.dk/html/gal_vis...2166&ipc=18843