I got my 9XL today and hooked it up to the MMM. As there is no flat spot on the motor, I had to grind one myself. With the the RC-Monster heatsink clamp, I am not able to position the pinion onto the motor such that it will make full contact with the spur. The flat side of the pinion is towards the front of the truck. If I flip it around, the grub screw does not make contact with the shaft. Without the heatsink I don't think this would be an issue.
I have it geared 24/56 right now and I ran through my *****-K 3000 2s packs without any major damage. I did flip it backwards and had it slide down my street for 30 feet, grinding a hole in the roof, however. I also lost two body clips in the rear. Other than that the truck held the power well... oh the power.
It was difficult to use full throttle with the truck now. Even in the grass, where I did most of my running, it was blisteringly fast. Wheelies are a quick pull of the trigger at all but the fastest speeds. Without a good safe place to run, I was unable to top it out. You people running 40-50 mph are nuts. I'll have to add some punch control as it's currently zero. Start power is medium, timing is normal.
Temps were a mixed bag. ESC was 120, batteries were 125, motor was 205! The heatsink is not doing a very good job, as it was 75. I spread a very thin layer of thermal grease onto the motor and heatsink, but I may have used too much. I'll wipe off even more and see if I can get it to make better contact. At this point the heatsink is acting as an insulator.
Overall I'm very pleased with the truck, and that's just with a pair of 3000 mah 20C packs! The 4300 20Cs are up later.