BTW, a flying buddy just finished an Edge ARF with a BIG 4 stroke in it. The cowl had two huge openings. The engine happened to be mounted at 180degrees however. And he had only cut the cowl to clear the front part of the head. Basically, the front of the engine was shielded from the airflow. The engine ran like crap. He wanted to know if I thought he had the wrong prop for that engine or if it just wasn't a big enough engine. It was touchy, ran rough and didn't seem to have much power for a 1.50FS. My advice was to open the cowl in front of the engine and close off most of the gaping holes that weren't doing spit. Darned if he didn't take the advice. Bloody engine runs like a locomotive now and the airplane is trimming out to be an excellent flier. And incidently, he's running the same prop.