I really dont care for the GPI or grains per inch of an arrow I am more interested in the spine of an arrow.
You can get some high GPI arrows that are weak on spine and people think because their arrow weighs x amount it is good to shoot then wonder why they have so much trouble tuning their bows.
Pick a spine that is suited for your bow and go from there or you can be like me pick a head weight then design the arrow around the head
