I'm using the sqare section belt from an old VHS recorder, to drive the governor on my resently restored Stuart Turner S9. I'm proposing to use a leather flat belt to drive a generator from the S9, that from the engine to a lay shaft, then ??from the lay shaft to the generator.
O-rings tend to slip if required to transmit any power, I use the heat joined belting on my hot air engines, it drives generators, or my little power hacksaw, or a water pump, its great. Ian S C