My TT is nowhere near in the league of yours, but my shelf is similar: a Synergy Twin 40, with the TT placed on the double-width top shelf. These racks don't really qualify as primo TT support, to say the least - of course they have their other virtues, relatively speaking, but although not horrible by any means (especially compared to Salamander's Archetype series), the adjustable frame is far from maximally rigid, and the MDF-core shelf is fairly resonant. In my system, I use a Symposium shelf placed underneath the Technics SL-1200 'table, supported by four FoculPods soft sorbothane footers sitting on the rack shelf. This has worked well for me, but my TT's built-in suspension presumably is not as effective as yours. With this arrangement, physical energy inputs to the rack's frame or the shelf are greatly attenuated when felt at the Symposium, but I have honestly never sonically compared this set-up to placing the TT directly on the rack shelf. Although I don't think you can really go wrong using some kind of non-resonant shelf, such as the Symposium or one of the others, you may also have to experiment placing it on hard footers like cones in order to avoid excessive motion resulting from multiple soft suspensions. But whether you'll get an audible improvement over your non-problematic current set-up, probably only trying something out for yourself will tell.
