I don't know why I didn't catch this thread of yours earlier. I could have shared some important info early on for you. But better late than never I guess so here it is...
I was working on a chopper project of my own earlier this year. It's a Giant Stiletto for my brother. He likes riding the bike but it's difficult to ride in the steep hills where whe lives. Some of those steep hills have up to 15% grades. You practically have to pedal standing up and that's not cool nor comfortable on a chopper bike. So I "electrified" the bike so he could enjoy riding it around all those steep hills.
For the electrics... I chose to give him a BMC V2-T (torque) motor, a 18-FET BMC controller, and 12s LiPo batts (44.4v nominal, 50.2v hot off the charger). I mounted the controller and the batts on the bottom tube.
For the wheels... he had a 24-inch wheel in back and 20-inch wheel up front. I know a hubmotor up front on a chopper would feel sluggish and terrible for steering so I decided for a rear hubmotor. I bought a 3" wide black anodized rear rim (as an upgrad from his original 1.25" rims; fortunaltely I was able to find one with 36 spokes). I bought the black spokes and had them cut to the proper length, then laced up the BMC V2-T motor to that 3" rim.
For his brakes... he originally had 6" disc brakes. Fortunately the BMC motor had disc brake mounting holes allowing me to keep those rear disc brakes. But I also upgraded those brakes to a larger 8" disc and better Avid BB7 brake calipers.
Anyways, I've yet to finish the bike but here is the results on the day of the initial test ride...