Adb, I'm out of town for the next two weeks, but I'll upload a pic of the spine tester I came up with when I get home. I cut my own shafts using Veritas dowel cutters both 3/8 and 1/2". I worked my way through poplar, ash, white oak and finally hickory in both sizes, put them on the spine tester and marked their deflection, I then shot them to see which worked the best. (I measure the raw shaft on the 1/2" before i taper to 3/8", and I measure all at 33" overall length) Currently I shoot 3/8" poplar on my #90, 3/8" hickory on my #110, and 1/2 tapered to 3/8" on my #120. But like I said, this is just a scale I came up with, I don't know how it would actually relate to how others measure spine. I'm not really happy with the 1/2" arrows on the #120, I think they are still too heavy, but the 3/8" are definitely not heavy enough.