Another way to get a pretty close spine on your shafts is to drive two nails into the wall at about 12" or so. Take an arrow that flies well from your bow, and put the end under one nail and hang the shaft over the other. Then take a weigh, any weight, from the other end of the arrow. mark the wall at the point where it bends. Then, do a bareshaft of the same length the same way. If it doesn't bend to the mark, it's stiff, and if it bends beyond the mark, it's weak.