In general the ballance point for your tipical trainer wing is 25%-30% of MAC (mean air chord). Meaning measure the chord of your wing from front to back, let's say it measures 10 inches. 25% - 30% would then be 2.5 - 3.0 inches from the leading edge. 25% would of course be your more cautious setting. If the glide slope is to steep at 25% then go ahead and move it back from there.