Very surprised to see Peter from PBN saying it could make no difference.
If that is indeed what he said then it is no surprise to me. None at all. What he said was it "could" make no difference. Read carefully what that means is he ASSUMES and has NEVER TRIED.
That tape is very expensive per square foot but well worth it for what it does. First piece I tried went on the base of my Conqueror tone arm. It was only about 1/4" by 1" long. That was enough to hear improvement. Not a lot of improvement but 1", come on!
The thread here where I first heard about it they guy has bought many sheets and uses it all over the place. Tone arm, RCA and power cord plugs, outlet covers, circuit boards, caps. Does not dampen in the normal sense of things we are used to that suck the life and dynamics. This works more at a very micro level where it reveals detail by removing smearing.
Brass I think works more because it has a bit more stiffness and a better vibrational profile than mild steel. By that I mean it vibrates in a way we like. Which is after all why we make so many instruments out of it.