Besides using the manufacturer's often Conservative c/g location, is there a formula one can use to help predict the most desirable c/g? I realize that personal preference's come into play but I'd like to start closer to the correct location to cut down on trimming time. Buy the way I am talking about sailplanes in this case. I raise this question because in searching I have seen starting numbers from 35 to 48% of the root cord, compared to the recommended 30% in the case of my plane ( a Sailaire).