I'd have to say my maintenence bills for the YS so far puts the fuel bills to shame.

There's no argument that running petrol will drop the YS running costs if the maintenance requirements don't get worse, but I think YS would need to bump up the capacity to retain the performance. Considering that the crankcase is probably due for a redesign it might be the time for YS to consider a 2.20 sized petrol (with optional methanol kit), if they could keep the weight, heat and vibration under control.

There's certainly no lack of space in a modern F3A engine bay for a physically larger engine.