I got schooled by 3 Rivers spine calculator. Been having trouble shooting my first batch of ash arrows I made last week and shooting from a Spirit 66# recurve I recently acquired for an Elk hunt this coming Sept. I shoot cock feather in and it is damaging the cock feather slightly. After maybe 25 shots they look ragged some. Too stiff right? Little did I realize that the bow isnt cut to center and when I plugged that number into the Dynamic spine calculator it reduced the spine needed by 15lbs!!!!! I had no idea it was that much difference because Ive shot center cut bows my whole life. I shot some 2016's from the bow with 125 points and it shot a lot better than with my ash arrows. Lesson learned and noted.