Well, after what gluemaster said, and being 40SR a very powerful motor, with a lot of power to give out, I'm not pretty sure what I want, I want to have a dependable A/C and if I put that big engine then I'll need to modify the wing to fuselage attachment, the rubber bands wont do the trick, so I guess I'll need a smaller engine, not sure yet which one... because I dont know which other engines I have sitting around.