Mmmm...Good luck with your findings/project. Unrelated to your problem, many years ago on my newly re-built RGS, I had a tapping noise when riding which drove me mad for some time. Tried all sorts, stethoscope, screwdriver bunged up my ear, checking all fasteners. Rode it around the block and the noise stopped - yippee! Out for a real ride, the noise back again. Eventually, it only happened when I rode the machine with my Belstaff waxed jacket on. The culprit was one of the lower brass press fasteners vibrating against the Lyta alloy tank due to the position created with the clip-ons......