I've seen several planes lately that were obviously designed for a inverted two stroke to have a side mounted four stroke. Seems like it works out pretty well as far as what to do with the muffler? Also engines on their side are not as troublesome as the inverted ones.

I see one guy at the field with an inverted Saito 180, closes his high speed needle and opens it as he starts the engine. He has a L-shapped wire in it and keeps up with where the right position is. He makes it work and seems to have no trouble.

enjoy,
Jim