Right now my spine tester shows same as Gordons
I tried a spine tester like you mention that I made for wood arrows but 26" is just too much span. I just screwed a block to the side of my glass cut table, and use a spring clamp on 8" of glass past the block with another block clamped on top of glass. I used Gordons as a standard bend with the weight with marks for different sizes on side of table since Gordons is usually pretty close . The test seems to be pretty close to what to expect.