I side-mounted my Saito 150 and used an exhaust extension to hang the muffler off the landing gear. The cowl carving was long and complicated, but looks fine; notching the bottom of the cowl for the exhaust extension also took time, and looks okay. If I were doing it over, I would invert the engine and use the stock muffler, and install on-board ignition. In fact, I may just order a new cowl and do that anyway (but with a 180)!