What is the perferred material for a TT shelf?

My current solid and my previous suspended table both benefited from being spiked to a 2" thick maple slab isolated (with those ubiquitous) cork/felt constructs from a shelf of baltic birch plywood  screwed down tight to a pair of wall hung cantilevers. 

Improved texture and tuneful bass. The maple acts as a sink, an engineer friend tells me and the lightweight shelf dissipates the energy to the wall.

It might be true. At any rate, there is an audible improvement.

That would depend upon the TT you are using.

Sans that info any replies are clueless.

You guys have me thinking that I may have chosen the wrong material, or perhaps the wrong decoupling method.  Am I better off with a large set of spikes under my acrylic than I am with the Herbies Audio Lab Grungebuster Dots?

I have the Michell Gyrodec which is basically a Gyro on an acrylic platform decoupled with aluminum spikes and aluminum cones as feet on the underside.  Seeing as how Michell chose cones under their acrylic, I'd say that is a good place to start as any.  If it doesn't work out, as least it's not too expensive.

If your table is a non-suspended design: Two shelves of Baltic Birch Plywood separated by a slightly inflated bicycle inner tube, with the table sitting on three roller bearings arranged in an equilateral triangle. The most effective isolation short of a Minus K or similar platform (which cost in excess of $2000).