Tor Stahl is a commuter that did his homework!
“Below is picture of the bike, it is a Spot Champa frame, which is made for a belt drive. The key to using a belt is to use a 3-speed IGH which is made to accept a cassette. I use the Sturmey Archer CS-RK3, SRAM makes a similar dual drive which I have seen used for the same purpose. I used your spider and spacers along with a 55 tooth front and 22 tooth CDX belt cogs. With the current set at 17, as a pedalec, I can easily travel at 30+ miles an hour on a flat, climb fairly steep hills at 20+ mph and still get plenty of range. I have about 50% battery left after my 40 mile daily commute with some decent hills involved. Motor only, the gearing is pretty high, but it will hold a speed once you put some pedaling in. The pedal clutch failed and I was able to motor home, but I had to push the bike up the steepest part on my commute, which is short. For me its perfect, I like to pedal. I use the 5 PAS levels as gears along with the 3-speed internal, giving it basically 15 speeds, I don’t know why you’d want any more gears.”