I think something that should definitely be figured into the equation is draw length. I don't think a low arrow weight/pound of draw figure hurts a short draw length archer's equipment nearly as much as a long armer. I don't think as much energy is being generated and transferred to the arrow with the shorter draw length as with a longer one. Hence the much lower speeds when 2 70 lb bows are compared. That is obvious to everyone I'm sure. I shoot just above 5 grains per pound and have a 26" gator-arm draw. There is no vibration or hand shock that I could tell. Just something to consider. I am not sure where the cut off in draw length is to start being concerned about grains per inch, but I would suspect it to be true at 29" and above. That is just a gut feeling, though.