Okay, I just tried it again with the lenses oriented like they were in the pic above (there were shadows of the shims still visible to help me do that), and the rings are way off center.
They're right on center with the arrows aligned, though. The shims look like they have a weak adhesive on one side, and they're all regularly sized - 1/4" long by 3/4" wide.
-Tim.
-------------------- "We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"