Spine and total arrow weight are two different things. Spine has more to do with the flex imparted to the arrow. At a 200 or 300 spine arrow it is too light of a spine, a light spine will flex too much and won't recover fast enough. It imparts too much flex which "could" lead to shaft failure on the shot with kind of poundage.How do you figure?
My total arrow weight is just over 500gr so I'm well over the gpi minimum, and a .300 spine as been used on bows well over 90lbs