The first test flight was completed with only minor damage to a prop and the spark plug cap. The engine is mounted inverted, and during taxiing, the tail jumped up and caused a nose-over, thereby destroying the prop and slightly damaging the spark plug cap. I failed to keep elevator up; it was my fault. The stainless steal cover on the spark plug cap split open. So, I just force it closed again with a plier and screwdriver. Fixed. Good as new. I haven't yet been able to get the engine to run at its full potential, but it has been running quite reliably. Hopefully, it'll get stronger as it gets broken-in. Is there a simple way to protect the engine, in case of nose-over? See how the cap is sticking out the bottom.