What is the perferred material for a TT shelf?

I went to my local acrylic workshop in an industrial area and had them custom make mine. It consists of two 1" slabs of clear acrylic. The top one has a channel routed out to the shape of an acrylic cover I had made so when it sits on top, it can't slide around. I used isolation dots from herbie's audio lab under the base layer and between the two slabs.  The look is beautiful and the functionality great. You can see it on my virtual system page.

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?