vibration and resonance

Both dynamat and cork stink.

Don't throw good money after bad. If your rack "rings", I suggest you go with something by the established manufacturers. I have a Salamander Archetype with cherry shelves that I am happy with, but would also look at Cambre, HRS and a few others if I was in the market.

Do you have the rubber washers between the nuts & the shelves like the salamander racks do?