Best type of metal for turntable platform?

I have a Townshend seismic platform (it has pods attached under it) under my turntable. When installed, it improved the sound so much I was incredulous. Unfortunately, the very low waves from the pods combined with my suspended floor and extremely light turntable created footfalls that didn't exist before (to anywhere near that degree). 

It was either live with the improvement and tread lightly or go back to square 1. I was going to live with both because of the sublime sound. But, guess what - I put in a wall shelf ($179 from Project) and put the Townshend platform on top of that. All problems solved and the sound improvement had to be heard to be believed. I was very skeptical.

I like the platform better than the individual pods because there is no fiddling around with placement. You can adjust the springiness in each spring to level the platform for items that have lumpy weight distribution.

@millercarbon takes a lot of abuse from some posters, but I have to thank him for turning me on to Townshend. I had the privilege of talking to Max himself a couple times - extremely nice down to earth guy, very honest - kind of like a mad scientist who does his own research and has solutions that work. When he starts talking about continuous earthquakes, he is on to something.

Wall mount, better shelving/ rack- 
better table, feet - so many options , solutions 
Many May cost less than suggestions so far-
Have had problems w “footfall vibrations “
Better turntable, racks, footers, cartridges, have helped for different situations.
From my perspective, no one size fits all

As in most of life, there is no best anything. 

Of course not. But I think SME tables take care of everything (no shelves, pods/platforms, etc.,) from what I've heard. Not inexpensive though...Sound like an end game for the whole source discussion.

Given that you can have your own platter machined you should do the following:  It should have a hollow space underneath.  Think Technics SL1200 platter.  It has a flat top (of course), and then at the edges it has a lip (with all those dots).  Underneath is a rubber underlay.  Do something similar but rather than a rubber underlay you will pour epoxy (g-flex is good).  This will damp the platter.  This is important if you are having a metal platter, otherwise it will ring like a bell.  The constrained layer damping suggestions are also good.

As regards footfall I have two suggestions.  First add some mass.  For example I use a one inch slab of granite on my shelf.  Second get some aftermarket footers.  There are maglev footers on ebay,  Even better are Isonoe footers - they are in effect mini trampolines.  I can jump up and down next to my TT without adverse effect.