rcpi:
I'd be greatly interested in your experiment.
I have a BOB trailer which I've been meaning to drive with a motor. In a flush of newbie excitement, without considering the controller options, I ordered an outrunner (HXT 80-85B which has a nicely manageable 170Kv) and other components to gear it down including a #25 final drive without a freewheel so that I could use braking/regen to control the trailer.
Upon reading more about the Phoenix controllers, it looks like braking is best left turned off. And of course, as discussed here, none of the other BLDC controllers (like the Kelly ones) support the "sensorless" mode.
So, my options are AFAIK:
1. get a new high-rpm brushed motor (like the Magmotor, S28-150) and then get a regen-controller like the 4QD or Kelly ones,
2. change my final drive to use a freewheel, forget about motor-braking, and just go with the Phoenix controllers,
3. (and this is news), Kelly is supposedly working on a sensorless controller which should be ready in 2 months,
4. hope for a Hail Mary in terms of retrofitting hall sensors onto an outrunner.
I should mention that I am using a front-wheel brake disk hub for my trailer's single wheel, and attaching a 80T sprocket to the disk-mount, which is why motor-braking (with or without regen) appeals to me.