The method of using 1/3 of the chord at the root is not a very good way to balance. The shape of a wing has more than just a little to do with balance point. If the leading edge is swept hard {F-20 tiger shark} as apposed to a straight leading edge {EDGE 540} the 1/3 rule will not work. I have been flying pattern since the 70's and TOC for the last 5-6 years and I can say without any doubt the plane will fly very differant at 30% than 33% MAC. Also the smaller the plane the more CG affects its performance. If you are serious about building and flying, a incidence meter and a balance stand are as important as an razor knife IMHO.