Just ordered some Easton X7 cobalts in 2613. I see glue in target points offered in a variety of different weights and I am wondering what will work best for shooting spots with my setup. I shoot a Quest Primal 29", 70# draw. I ordered the cobalts so I can use my FOBs with a target arrow. How many grains should I put on the front to have the correct spine?? Thanks.