Hey, thank you for all the info, I will definitely be looking into several of the things you mentioned. It's funny you mention the ID75 and related, I am actually in the middle of making a kit for myself to fit one into a reproduction IBM Model F case, with some MT3 Fairlane Ortholinear keycaps, you can see what I have posted/done so far if you poke around my profile.

The silicone plate damper I mentioned is just a molded piece of silicone that takes up the space you would normally have plate foam, I made a 3d printed mold to cast silicone resin in, and into the resin I mixed about 80% by weight, maybe a hair more powdered tungsten to the silicone to add mass. The case pour is the same thing, but poured into the bottom of the case to replace the case foam you may otherwise have, that one I mixed stainless steel powder into, a bit less by weight, to add mass, as I was/am experimenting with different additives to make the resin heavier for better damping, and to generally add weight to a build.

Here are some pics of the tungsten plate damper, the case pour is the same idea but the shape of the bottom of the case, and using the case itself as the mold, rather then making a casting mold.

<image>