First balance the blades. Put tracking tape or scotch tape around the far end of the blade until it balances equal on your balancer. Then take the original heavy blade and find the c.g. Mark it with a felt tip pen and then lay the light blade next to it and transfer the mark on the light blade to coincide with the first mark. Now take scotch tape and place it over the mark on the light blade until the c.g. matches the heavy blade.