...too much mass....

Brass is over 3 times as dense as aluminum. Bobby Wolfe had a brass spider he said was cast by
Tut Taylor to answer your exact question. The effect was just as Docslyd said: very quiet sound, much like adding a heavy mute to a banjo bridge.

+1 to Eric and Sam on brass spiders.

Once upon a time, Brad Harper did some experiments with carbon fiber spiders. The results were underwhelming.

Aluminum (of the proper alloy, in a "#14" style casting) has been the way it worked for Dobros since almost the beginning. It's great to experiment with different materials, and I'm sure we will hear it here first if there's a breakthrough.

Hey folks...Jack Stepick....luthier in Newton NJ and I experimented with making a 3 leg spider...thinking along the lines of the "milk stool" that always stay level. Jack made wooden version...I made a 6061 aluminum version. Both did not perform as well as the 8 leg original design. I believe the original design was made "half round" to release it from the mold. I think an 8 leg spider made from "tone wood" might change the dynamics...and add some tone differences. Jack and I also discussed adding a second cone...piggy backed in the cavity. I experimented with gluing a second cone to the inside back of the guitar and having a 2nd cone in a usual location. I will say the sound didn't improve in volume or tone, actually seemed to cause a second over tone..."a wolf tone"...if you understand cello wolf tone suppressors.
I guess we all attempt to improve our playing with "Gadgets"...real question is "Can you play the instrument"? Jerry Douglas could play a $200 Rogue or a $10,000 Tim Sheerhorn and still be at the top of his game.
No reason to stop thinking about ideas and p[ossible improvements...sort of like Chevy's and Rolls Royce both will get you to where you're going.
Smile and Be Well,
Tom

I think we may have worn out the alternative material spider for the time being so I'll add a comment after reading Tom's post above.

Tom, you mentioned a second cone experiment. Paul Beard got it right when he came up with the Belle Beard.

 Of the celebrity players, the two I know of that play this model are Cindy Cashdollar and Andy Hall. Nice review from Tony Polecastro.

Boron fiber composites are the answer to the ultimate spider construction.

(now we wait and see if someone takes the bait and figures out to use it and how it sounds)

Out of curiosity, I once built a maple T-bridge for a Tricone. The tonal difference compared to an original bridge is very small. But that’s probably just my ears, because some people even claim you can hear a difference when you remove the black paint… :)

http://www.youtube.com/watch?v=gij3ELDITpI