I know you can't enter bow speed in Stu's Calc. But just for funzies, I wanted to calculate arrows based on my measured bow speed. I was able to do this by adjusting the draw weight for my bow. Once I did that, the best flying arrows actually spined within 1 pound! I don't know if I should have did it that way, but if it works, Stu's Calc maybe needs an input for actual bow speed? Anyway, it was quite interesting.