A Copernican View of the Turntable System

Halcro,
Makes sense as an inexpensive DIY solution. May not be as pretty as the DaVinci solution but there is no reason why it cannot be made reasonably pretty. The question I would have is how one can make really decent Micro-Seiki-like armbases to fit in the middle of the top plate, and have the top plate look really, really good.

The only way I can think of it is to make a very fine liquid "top" by turning it upside down (so top is down) on wax paper and pouring only the first 2-3 cm (with a styrofoam blockout for where the top plate and VTA tower will be). Then after that is done and mostly dry, pour the rest in around the blockouts and let dry. The first layer on wax paper, if wet at the very bottom, should create a super-smooth surface which can be finished as one likes.

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.