There is a guy flying QQ''s Yak this size with an OS .32sx and it is plenty of power. I''m thinking of the Saito .40a four stroke for the torque. I read a thread about a guy using this engine with a three pound plane and it hovers good with an APC 11x5 prop. The engine weighs about 10.7 ounces so it''ll weigh the same as the electric version. If you wanted to add five more ounces, you could use the Saito .56 or .62 which cost about the same.