Measure the cord at the wing tip. Then divide 2" by that cord to get the %. Then multiple the cord at the center by that % to get the distance from the LE. For example:
Assume your wing has a tip cord of 5" and a root cord of 10". If the balance point is 2" from the LE at the tip it would be 2/5 or .4 = 40%. Multiply the root cord by 40%. 10 * .4 = 4". So the balance point would be 4" from the leading edge at the root.