Re: airplane bought at auction=it looks like an EU1A with the anhedral stab. In any case 25-30% back from leading edge average (called MAC for mean aerodynamic cord for C.G. and 1/2 to 3/4 inch on el and ail to start. rudder approx. 1". Remember, the further aft the C.G. the more responsive the airplane. the further fwd the more stable. 25% MAC for a pattern ship will give excellent stability and the smooth gracefull lines of the old style for which this ship was built.