Ever since Jersey Jim Martin suggested avgas in my 30cc gassie, that's all I've run in them. Octane is 100 which some think is high but in my experience it works great in the small gas engines. It reduces power ever so slightly compared to premium auto gas but the power is smooth and pure, and is plenty for an 11 lb pattern model, as I've stated before. My piped OS GT33 on avgas turns at least the rpm as the YS185 does on 25% nitro on the same prop. The 185 might have a slight edge in mid range...not that the OS mid range isn't very good. I never have to lead the throttle in any vertical. Just point and add as it needs, same as any good electric or good YS set-up

As I said earlier, either powerplant could benefit from lightweight belt reduction, 1.2:1. A 22x12 at 62-6300 would be sweet.