A 12/51 gearing is low, so it may help the motor out. Guys doing 10s systems are using 1400 kv motors and low gearing. Of course those are high end motors, but the same may be true for the feigao. We can all agree that an xl motor in a rustler would never get very hot, just not enough load on it. So relieving the motor with lower gearing may help the heat situation. Let us know what you find. I may try my 7xl on 5s(wow)! In a tower terror mt!!! 10lbs or less!
I had to have one, looked good on paper. I have taken it apart and it is stout, diffs look really sturdy. Truck is light even with the 7xl in it and 4s lipo. Simple too, good steering like an 1/8 scale buggy, and plenty of screws holding it together. I will post up info/pics when I finish.