Has anyone used the dynamic spine calculator on the #Rivers Archery site, if so how accurate is it? It was telling me for 57# at 28" shelf cut 3/16 past center, with a 30" arrow and 200 grain broadhead total weight 580-600 grains I would need a 250-300 spine arrow. This called for a stiffer spine than I was expecting to use. If you have a similar set up with your bow and arrows what spine are you using?