I found that, for my install, the bolt was more than tight. But the metal cylinder spacer was too long and didn't let the gap close enough no matter how much I cranked on the bolt. Instead of over-doing it, I just solved the source of the problem.the easiest fix is to tighten the bolt connecting the bars, the one under the cooler. It does that when it's not tight enough.
Even better, remove bolt, add some rubber (i.e. from a bicycle inner tube) and re tighten.
I'll be throwing on the Shinkos pretty soon. I doubt they will cause the Givi bars to start rattling after I fixed the problem. Right now I'm riding on a squared-off Tourance* and when I turn (onto the tire's barely used outer edge) it's like riding on knobbies - I can feel the rumble of the raised tread on the road surface.Mine has it now that I changed the deathwings to Shinko 705's. Go figure?