i am thinking about picking up 6 of one of these two arrows to try them out of a classifieds. but im not sure what size i should get because i shoot 27 1/2 in arrows and at 27" in they suggest i shoot the 2-28 and at 28" they suggest the 2-39 im shooting a bowtech pro 40 dually at 60 pounds. which size would you all recomend?