After fitting 5-40 bolts to the OS MaxIII and cutting a new base gasket I finally resolved the issue of the head coming loose. I filled the tank(2oz) to see how many laps she would do with the new .281 venturi. I did 40 laps. The next flight I took off did about 3 laps then went inverted. Winds were pretty steady around 13mph. On my 3rd lap inverted the engine suddenly quit. I should have landed her inverted,but decided to flip her over to upright thinking I had enough momentum. I was wrong. The wind got her,blew her into a funny position,lines went slack.The plane went straight in from about 30 ft. I thought it would be destroyed,but the only real damage was to the outboard wing panel where the weight box came thru the leading edge. I'll fix her today.But.....why did I have a fuel delivery issue inverted??? PhillySkip