It's not about what you put under it, but about what you put it on ;-) And even if your "rack" is reasonably sturdy, the floor structure under the rack is probably what's bouncing (it's not a concrete slab is it!)Yes, I have an old house and my floors are not that good, but I've had other TT's that were not nearly this bad.
A wall mounted rack would be nice but I don't think it would work with the way my room is set up. Speaking of concrete slabs, would putting a heavy flat piece of slate or stone of some kind help?
Thanks for the info.