[bigendbob]

I spent 5min with a socket tightening those nuts..didn't make much difference, i think you are just pulling the surface further away from the folding top.
I found the whole deck area was moving up and down, and thats how the sticky pads cured the problem. Now is all silent. When the rear deck closes it must rest on adjustable stops, to make flush with the bodywork. But can still be gap where rear deck 'hovers' over the join between the plastic trim just behind the roll hops.
The sticky pads stop the rear deck banging onto the trim just behind your head.
I tried driving and reaching back and holding the deck down and thats how i found out it made a difference.
Remember the cabin is small and sound travel... a sound in my right ear turned out to be the tax disc holder vibrating over on the left!

And another irritant, sound like grit hitting windshield, actually plastic clicking around windshield area. Couple of sticky pads where sun visors touch trim cured that problem.

Getting there slowly.