.....maybe a RCS140, 3w24, roto35. Only prob is that for those size planes sometimes the gas engines are too heavy with the ignition and battery to be really worth it. You could make it fit, but the weight of those engines compared to a Saito 120 or 150 could be too much for the aircraft to be fun or easy to fly cause of the higher wing loading. Balance could be an issue too...

Tim