Originally Posted by reburns

I have used the method of strumming the belt and measuring the tone frequency at various rotation angles to find where the belt may be tightest, then simply loosened the ring bolts and retightened to get the tension fairly even over the full 360 degrees. I shoot for roughly 40 hertz, plus or minus. All very crude compared to your analysis. But I have yet to replace a BB since switching to the belt, although I did have to replace one when we had a timing chain.

I agree with others that the Gates recommended tension is way higher than necessary.

Are you sure the two rings are perfectly aligned, and neither is bent causing some of the axial runout you are measuring?