Hey Jim!
You can run a 52 volt with no issues..
My understanding is you gain a bit more speed like 4 mph,
not torque.
I added a 1000 watt front hub motor and a 20ah second battery...
This has doubled my torque,IMO.
I'm 6'3" and just over 300 lbs (for now anyway) and my bike pulls great! No issues with steep hills!
See you out there,
Cheers!
Racer