I have the seagull spacewalker II 40 and can't get the C.G. right. the manual says 7.5 to 8 centimeters from the leading edge of the wing. It has an os 46ax all the way at the end of the mount,5oz. of lead on the firewall,RX batt. all the way up front on the fuel tank and it is still tail heavy. ANY SUGGESTIONS????????