I bought an Aliexpress-sourced 20" rear kit for my EZ-1 & am struggling with wheel / freewheel fit. When I insert the hubmotor with spun-on-tight freewheel into the dropouts, even with 2 washers on the axle inside the frame on the freewheel-side, using the provided 7-speed freewheel, the 14T gear rubs the frame. I thought I could address that with a different freewheel with smaller diameter (teeth < 14) gear, or rebuild a DNP 7-speed 11T freewheel to remove the largest gear to be a less wide 6-speed, but haven't figured that out either.
The biggest nuisance & show stopper for me is seeing how poorly the wheel is centered within the frame when I have 2 washers on the axle inside the dropouts each side. The wheel is way over to one side. Just bugs me that I have to maybe do the "dishing" process of loosing / tightening spokes to effectively move the wheel towards the freewheel direction (as the kit manufacturer should have done) to properly center the wheel.