Same issue
Charles,
I had the same issue, while building and installing the rings I waxed them and set them in flox for a perfect fit. But perfect was too tight. I never considered Bill's "clocking". But I sanded and sanded and took a dremel tool to it until a "not loose" fit. You do have to be careful when painting that area. You do need a "non restrictive" fit or the two cowl halves will not freely come together.
Clocking? I assumed the rings were turned on a lathe and round, but thinking about it and knowing the rings were dropped on the floor etc. There might be a argument for clocking. But seems like just a little more sanding would allow a fit at any position and allow unfettered installation. I did rotate my rings while working on the fit. Even tried applying adhesive backed sand paper to the ring....but the tightness seemed to be where the male tongue fit in the groove and the paper did not help there, but the dremel did. Keep at it...