About spine and various longbows. It varies, depends on how an individual releases and any particular bow. Many longbows prefer a softer spine in carbon, when an aluminum is too stiff it will readily show bad arrow flight. However, some longbows will shoot stiffer aluminums and woods. I have one 55@26 bow that is 3/8" outside of center, a left or right hand duo shooter, the charts would say because of my 26&1/4" draw, 27" bop and its outside of center that it would that it should shoot a 40 pound spine. I tried a 40-45 cedar with a 125 grain head. It snapped and I got lucky. It likes 27" bop 1918s with a 160 grain point on a glue-on insert of 38 grains and 60 pound spine Doug Firs with 160 grain heads. I had a Big River 60@26 it was cut to near center and 2018s were way too stiff for it with any head, but 50-55s with 160 grain heads were perfect. I suggest getting or building three separate test spine cedar shafts from five pounds under to ten pounds over and do not cut them longer than needed. There a lot of great 160 grain heads that will soften the spine 5 pounds if they seem a little stiff.