Interesting. I've been considering a Bafang SWXH rear or Cute-100 designed for a 20" but fitted in a 26" rim and driven by either 36v or 48v (probably 36). Same kind of idea of trying to push the max assist speed up to 25 or so but with the smallest possible motor. I don't necessarily expect the motor to drive at that speed on the flat on it's own. I just don't want the assist to just disappear at 20.