I think the only issue on this plane with horizontal mount is that if you are using a sport muffler your probably going to have to make some mods to the firewall. Inverted engines work fine but you may need to make adjustments to the tank position. If I remember, the tank is already pretty tight and rides above the nose wheel bracket. I don't think my Dad modified the tank location. When filled, and not running, it does drip a little through the carb. He has not had any prolonged inverted flights so I don't know if it would be an issue. If you go inverted, make sure that you store with the engine head up or you will fowel the plug.