i think either the ervine or saito.i had a saito .91 on mine but had to put taller gear and bigger wheels for the 14x6.but it flew great.i never have owned a os but i think the 70 is much to heavy.with the .91 all i had to do was move the batt back to balance.but i lost her due to a tx failure.now the .91 is going in a ucando.46 as we speak