RE: Larger engine for a Extreme 540 by Goldberg
Don't you mean an Extreme 330 ARF? In my opinion that .60 2 stroke on that plane would be good for 1 thing....suckin up a lot of fuel. If you plan on doing any 3-D with that plane an O.S. 70 surpass 4 stroke would make it dance real nice in the air with plenty of thrust for 3-D flying.
Good luck