Hello George well intrested as You are building a machine for similar reasons,,
I Spent a couple of years building sound rooms for recording studios (in my spare time)You tend to find out what dampens vibration, Which is Dry sand filled tubes and walling .if the sand gets wet then it doesn't help at all.
Guts on masonry always under the table with a Drip check and should be dry when you look under when the machine is in full spray.

the overhead type even when the Gantry is 600 higher than the workpiece still gets covered in Abrasive dust and the rails wear quite quickly.
Ive seen at least 3 machines fail because of rails being on top or the side.
Humphries Masonry in Hungerford their machine right before xmas rails scored by a pieces of stone about the size of grass seed and all the carriages and rails needed replaced. Blooming expensive 3 metre Kolb machine

I had a look at a machine which uses 120x60x3mm 2400 on x and 1200mm on Y
this machine also had Hexagonal rails and v rollers on the X with 45degree 45mm v rollers on the Y and Z. I cant find Hex rails on the net it all seems to be profile which Jazz suggest.