I have a 6 space rack that I like to use with a couple of different cabs configurations. When I use this rack on top of 2 Aguilar GS112's, the rack produces a very audible vibration noise. I don't seem to really notice this with other cabs but that's probably because I'm generally playing at an overall lower volume with the GS112's - and that makes the vibration noise more noticeable. I know that taking the rack off the cabs will solve this problem, but I like the rack to be up high enough to make adjustments without getting down on the floor. Anyway, I'm thinking that trying a Auralex Gramma on top of the cabs / under the rack may solve this problem. Has anyone tried something like this?