I haven't tried a massive brass plate, but I'm not sure it would be awesome. I would think it may have more of a tendency to ring or resonant sound on it's own. I could be wrong, as I know some have turntable's with 75 pound brass platters and no complaints. However, I'm happy with 2-3 inch think slabs of maple wood with brass cone footers.
Cheers,
John
Cheers,
John