as far as I can tell, it's pure aesthetics. Mainly to clean up the lines that are visible above the cowl--to look more scale. It isn't performance. In fact, care must be taken when inverting an engine not to flood it. Once running, they pretty much run the same as normal-mounted engines, but some need onboard glow to help with the idle since the fuel can more easily get onto the glow plug and cool it off.