arrows are spined based on a 28" length from the base of the knock to the base of the point. As a rule of thumb, if you cut off one inch, the actual (dynamic) spine will go up by 5#, so an arrow marked 50# for 28" will actually shoot like a 55# spined arrow if it is 27" long. For a 26"arrow, you could use -10# as a starting point. If you are shooting a 50# bow, you might start with 40# spined arrows. However, there are so many variables (point weight, degree of offset of rest, fletching, etc) that you just have to test them a lot. If you are like me, the real problem is just shot consistency that have a greater effect than spine.
