Best type of metal for turntable platform?

I always thought copper would be cool. Trying to find a billet that big may be a problem...

I'd try a damping material between two layers of aluminum.

There are so many divergent theories on what an ideal platform for a turtable should do, and how it should be made. I've noticed lately that for high mass and unsuspended tables stainless steel has been popular. What turntable(s) are you going to use on this stand?