My form must be terrible because I keep getting told to drop spine on arrows for my weight and draw length. Usually between 45-55#@28.
90's, 3355's, and 150's did nothing but frustrate me. Carbons I have left are GT 5575 with 300 front, and they work fine.
90% of the arrows in my rack are either bamboo or woodies and they all spine out between 65-75#.
When I need to weaken them, I add # up front.
Go with what works for you. I may lose a bit of speed, but they land where they are pointed with authority.