A Copernican View of the Turntable System

T-bone,
Not sure I follow you on the tip-up and down bit?
If you want a glass smooth finish on the concrete?.......that is normally achieved by steel trowelling which is why I suggested screeding of the top surface with a metal flat edge as in a steel rule.
This will be equivalent to a steel trowel.

Otherwise, a machined metal top-plate to fit on top of the concrete, ensures a "really really good" finish.

Yes, you are probably right. The nest way to deal with the top is have a full-width metal top-plate.

T_bone, Why not use an actual M-S armboard (if you are using an M-S tonearm)? I think reproductions are made.

Halcro, You are obviously an architect. (I already knew that.) But doesn't all cement shrink to at least some degree whilst it is setting up, no matter how low the water content? And wouldn't even a small amount of shrinkage cause the inner cement cylinder to pull away from the walls of the metallic tube? Thus, could the cement cylinder become loose and actually fall out of the tube?

By the way, this issue of "shrinkage" was covered in a Seinfeld episode.

Lewm your comment on the cantilevered arm board pod was visualized completely.

It's just another design method that would be an easy build, fairly inexpensive and very convenient with use.

More importantly emphases are on further isolating tone arms from imposing colouration's including help reducing vibrations of all sorts by way of experimenting with arm board material type.

Dear In_shore, What you say is also well and good. I further still maintain that the tt and armpod ought ideally to be in unison, so use similar strategy to isolate both tt and tonearm, a la the Da Vinci. I would not favor using a Da Vinci or similar armpod with a tt that was sitting on AT616 feet, even though I know that others here are doing something akin to that and getting what they interpret to be great results. I think that might mean that the level of our concern regarding structure borne and internally generated forces amounts to massive overkill.