DD hubmotor sizes are quoted in terms of the stator diameter and width.
Like I stated in my PM you should take the quite easy measurements of phase-to-phase resistance, no load current, and Kv. You can do all that with a single 3 phase controller. You can even try it out with one controller with the understanding that performance will be slightly less than half. Just take care to make sure the unused set of phase wires don't short together, and take care not to lose track of which halls go with which set of phase wires. I wouldn't try to go highway speeds on one controller, but mine is pretty darn zippy running on just one. Takeoff with one trap controller isn't as quiet as with 2 and just under half the torque are the only differences, since it's 2 identical 3 phase motors in one with a 15 degree timing difference between the 2.
