Just a thought about your engine slowing down when inverted, may or may not help but try riching it about a click or two.

A neat way to learn inverted flight is to start with a loop and just before you get to the top ease in a little down elev. after a few tries you will get to a point that you can hold it there. One thing to remember when learning inverted flight, ALWAYS roll out, never pull out. If you pull you may just drive it in the ground --- you shouldn't be that low but --it happens. ENJOY !!!! RED