TimC, I did use a brass spinner nut, I still had to put the engine pretty far foward on the mount. It is set up at 4", with the aluminum spinner nut it sets at 4.75", but I will not be flying it set there for a while. One more thing this little plane just floats, the first couple of passes I made I couldnt get this plane to stop flying, it flys a lot slower and with a lot more control around stall speeds than my trainer style planes. Its great.