Another thing to consider with inverted mounting is access to the glow plug. On most 4-strokes it is angled back some, and you either have to make sure you have a straight enough shot to the plug for your glow starter (sometimes the firewall bottom can get in the way), or use a remote starter socket, or if you use an on-board glow system, (not really necessary, but nice) that will take care of it , too. I'd opt for the remote. You can locate it back from the engine area, don't have to reach near the prop to remove it.