I recently purchased a Black Widow PSA 60"45#@28 that I draw 30"(~51lb) and have noticed that it needs a much stiffer carbon spine. I have some mfx classic 400's(31" long 225gr up front) that bare shaft perfectly when I shoot a B-50 string but when I switch to my D-97 string, they fly almost sideways(weak). Now I am considering some 340 spine carbons, which I would have thought were way too stiff, but after seeing the 400's fly so weak, I am reconsidering. I know I will have to try them myself to know for sure, but was wondering if any of you have shot the 340's from a similar setup?