I run a 41 on mine but I usually coast at 15-20, I like the quiet-zero vibration ride, I'm not looking for speed, I like when people see my bike and able to stare. and I live close to senior communities, so I see a lot, I mean a LOT of 75++ years old drivers around it's scary.
I weight about a buck thirty and I can let the engine pull me from a start without pedal assist unless I have to start really quick plus I pull my daughter's trailer so I need the torque also.
Have fun
JD