On a four stroke, make sure that the prop is not a real tight fit on the prop shaft, ream it out a little if you have to. It should not have to be threaded on the shaft but should just slide into position. Now, if your four stroke kicks back from being too lean, the prop nut will just loosen a little and the prop will freewheel on the motor shaft without getting thrown.

Don't be afraid of four strokes, I shied away from them on my first models because the gurus all said that beginners should stick to the "more user friendly" two strokes. Two strokes indeed are user friendly, in fact, I saw no need to own an electric starter to get them running.

Today I have a couple of four stroke engines and I still don't see a need to own an electric starter. They just aren't that hard to use.

Four stroke advantages; nicer engine sound, excellent and linear throttle response, and you don't have that big ugly exhaust system ruining the appearence of your plane.

Bad points, sometimes it's hard to get them to idle slow enough to not taxi, especially on areobatic planes that have the ability to do almost unlimited verticals. Also, they are actually louder than most people think they are.