I think it's safe to assume TCS will limit the pinion to 20t max. It's very easy to check on the M07. The little hatch covering the pinion just pops right off.

Weird thing from my build - tried using the heavy duty rear axles, like you'd use on any other mini. They caused a very slight binding for some reason. I tried removing shims, different bearings, different set of he axles, etc, but the only way to get smooth axles was to run the kit ones. The funny part is I can't see any diffrence between the old and new. Weird.

MORE: Motor fitment is a bit of a pig. Ended up filing a little bit to make room for wires for Hobbywing 13t style motor. I'm guessing at some point, someone will come up with a replacement stiffener bar for that spot that's bent differently. Fitting the rear suspension mounts requires minor juggling abilities. Oh, the thing with accessing the gearbox by undoing 8 screws also requires popping off upper links, steering links, swaybar link and dampers. I think you could do some work with just the screws out, but it's tricky.

Still, I like this car so far. Nice plastics, stiff chassis. Still pondering shorty battery attachment.