I've learned that tuning is anything but predictable, and there's nothing quite like the joy of a bullet hole through paper with your set-up.
I just found success after being baffled for months. I shoot a 51# at 30" (my draw length) SR Swift and, based on arrow spine selection charts and the experiences of others, I've been trying to get bullet holes with paper tuning with 31" 2216's with various point weights, but haven't quite been able to get there.
Anyway, I should have tried this before, but I recently bought some 2219's to accommodate some new 60# at 30" limbs that I had Bill Foreman make me for the same Swift riser, and while trying to tune the 2219's for the 60# limbs, I also tried them (with a 175 grn. point) out of the 51# limbs and, viola, I get bullet holes with arrows that I thought would surely be over-spined for the 51# limbs. Turns out that the 2216's were under-spined for the 51# limbs all along. And now the 2219's are kicking tail left out of the 60# limbs with 125, 145, 175 or 200 grn points. I probably have a sloppy release that lends to the problem, or perhaps the center shot riser is part of it. Guess I'll have to try 2317's for the 60# limbs. I also wonder if I were to add something behind the vertical rest plate to move the arrow to the left on the shelf (RH bow), if that would decrease the required spine and help tuning for both the 2216/51# and 2219/60# pairings? Ah, but it is a labor of love trying to figure it out!
Lesson learned: think outside of the (spine selection) box when tuning doesn't work as advertised.