Inverted engines, need advice.
The only real problem you might have is a rough idle like you said. It seems that with the fuel falling on the plug, it wants to cool it off a lot more. Make sure the idle is set perfectly as downunder said, and have fun. If you have the weight/space to spare, you can look into an on-board glow driver, or make one on your own. With some creativity, you can make it light when the throttle is at idle.