RE: B50 vrs. Dyna 97
I' m going to assume your arrows are 28" BOP, with a 125 grain tip. I believe you' ll find you need a spine of around 80 lb. So many variables affect spine selection, it' s difficult to make a guess without knowing all the details of your set-up. But yes, a non-stretch string does require a stiffer arrow. I have been doing some testing lately, and discovered an endless loop string (as opposed to a Flemish twist) also requires a stiffer arrow. Enjoy your new bow!
Darrel