If your looking to isolate a TT especially with spiked feet, I've been experimenting with 1" thick plate of aluminuim braced on the bottom with cross bars of 3/4" square aluminuim. I've had some great results so far as a top to DIY sandboxes. A couple of manufactors will cut plate aluminuim to size for you. A 20x24" plate 1" thick cost me about $200 delivered to my door.
Sorry to not answer the thread question. I really do not know about the brass.
Sorry to not answer the thread question. I really do not know about the brass.