Over&Under,
I was waiting for someone to ask about the 3555. The answer is, I don't know. I know very little about tuning a bow, I shoot what works for me. I do know that the arrow spine charts say that a 3555 shouldn't fly out of my bow. My friend Mike set up those arrows for a 60# Griz I like to shoot, and I tried them out in the Fedora and they worked well.
My best guess is that my draw being 27.5, the SS Razorhead being relatively light (@100 grains), and the versatility of the GT arrow, combine to make it work for me.
Tom