I am in the midst of making a set of 12 longbow wooden arrows. Currently they weigh between 408 and 351 grains. The balance points are all just in front of the ideal, meaning the front is slightly heavier that the rear section. I am hoping that using a lighter point, 100 > 70 grains, on the heavier arrows will reduce the weight and move the balance point back. How much will this adjustment affect the arrow spine? The alternative is adding weight to the rear section of the arrow. Any suggestions?