I used neoprene rubber sheet (same as the way Ed Martin used on their installs) and had zero noise.Very interested to hear the report!
When I put one on my 200 Land Cruiser, it squeaked whenever the body flexed because the tank was mounted to the frame, but snugged up against the underside of the body.
I dropped it down a bit and inserted little rectangles of HDPE sheet (starboard) between the tank and body.
It has been silent and has worked flawlessly ever since!
Easily one of my favorite mods on the 200.