an arrow leaving the rest has to PUSH the tip (weather it is a FP or BH). Pushing a 75 gr point to 250 fps requires less force than pushing a 125 gr point to 250 fps. When the arrow is slung forward it bends, a heavy point on the front will make it bend bore than a lighter point. So if you have an arrow that has a weak spine, to some degree, you can compensate by going to a lighter point.

AH