MUST, I REPEAT, MUST, have two torque arms on a front drive! AND pay attention to what size hub motor. I've had a home build customer with a Townie and a 750W DD hub and no problems in 4 years HOWEVER, he doesn't use region braking and is pretty conservation. 20-24MPH max. If using regen, I install two torque arms in two different directions, if you get my drift. So there's protection in both directions. That said, ALWAYS monitor the allow dropouts.