As one of my old instructors told me, it's your plane, you can do anything you want to it. I agree with Jester about the muffler but the last one I built was the CG Cub and the fellow I built it for really loved that cowl with the scale engines molded in. The engine was an OS .91 surpass four stroke and got mounted inverted. I mounted the tank low and there are no problems with flooding or idling. Four strokes do tend to run better then two strokes when inverted but if the tank is located correctly then a two stroke is no problem. Just a choice thing and it's usually easier to mount and engine on it's side for most people. There have been millions of Cubs built and the engines have been mounted in every position the 360 degrees will allow. It's not a deep thinker, just a choice.