" The best way I've found to figure that out is to bare shaft tune them (if you haven't already).
I'll take the arrows that I think should be in the right spine category, add the tip I want on a full length shaft,
then shoot them with no feathers at 5 or 10 yards.
If they tail to the right, they're too stiff, so try adding more point weight.
If they tail left, they're too weak. Cut them down, starting a half inch at a time from the nock end, and repeat.
you'll see them get closer to straight. When you're getting close, only take 1/4" off at a time. If they're cut down as far as you can get them and still spine weak, try reducing point weight. (this doesn't seen to have as much effect on super stiff arrows). If it still spines weak, then you need to get a stiffer spined arrow and try again.
Once I learned how to do this, it DRAMATICALLY improved my shooting. Charts only do so much good, there are several variables that they can't really account for, and self tuning them is the way to go in my opinion."