It seems like some people on here have used Ponoko.com to have their plates cut. I've seen a few people using their Acrylic, and a few using plywood, etc
I've done some searching on GH, and I've read a bunch of discussions, but it's hard to decypher what was based on real results, and what was just brainstorming.
I don't think its worth discussing metals, as there is no question as to how well metals work. I'm mostly interested in results with 1.5mm materials (to keep the click-in benefit of the MX switches), because it's pretty obvious that you can use any thickness of most materials if you are willing to glue/friction-mount.
Acrylic - most people say 1.5mm is too fragile, some people suggest a 2nd lower plate with larger holes to support the upper 1.5mm plate, has anyone really done this? perhaps by gluing them together? or perhaps no support-plate, and just used lots of standoffs/legs to support it?
Delrin - is 1.5mm too flexible? do you need lots of standoffs/legs to keep it from sagging over time?
Silicone - same concerns as delrin?
Plywood - is 1.5mm too fragile? perhaps the same solutions as 1.5mm acrylic (support-plate, or lots of legs)?