My new tap arrived, so I drilled out two of the holes on the Castle Creations MMM motor and tapped them out to M4 size. Mounted the motor using M4 screws, modded the rear mount to fit the MMM motor. Now everything is rock solid.
MMM 2650kv motor endbell, nice sharp tap and the proper size drill.
Drilling out the holes, the material was pretty tough, I hope they are using 7075 aluminum.
Holes tapped, now I am checking to see what length screws I should be using, too short and they don't thread in far enough and can strip out, too long and they will hit the coils inside the motor. Notice how close the new M4 holes come to the inner alignment ring, just made it. Also, the bearing is gigantic.
This is why I went thru all the trouble of tapping the holes, M3 screw on the left, M4 in the middle and on the right.
All done, absolutely no flex in the mount now. M4's look nice sitting in the mounting plate.