Weight, Clamp or stabilizer?

For a platter mat, you could look into the Herbies Way Excellent mat. 
They’re made extremely well and can be ordered for any turntable. I’ve had mine for a few yrs now, and I really dig it. 
You could also check out an Achromat, which are very high quality as well. 

I posted before, that I put a stillpoints clamp on my Avid Acutus Dark, and no longer do so. This is because the clamp made the sound somewhat duller ... lost its musicality and airiness. In my system is a waste of £400

I found PL-560 feet here, for anyone else who was searching,  https://mnpctech.com/pc-computer-stereo-desktop-case-feet/technics-turntable-replacement-custom-feet/pioneer-pl-560-pl-540-pl-518-pl-516-pl-514-pl-512.html

Set-up. You can do a lot with set-up, and it's mostly free.

I am interested in the questions from the OP. I also have a vintage Pioneer table (PL-530) I bought new in the 70's. Have used different cartridges over the years and am now using a Grado Gold.
Aside from playing less than flat records I have an interest that pertains to the table feet. The feet on the PL-530 are just plastic ones that have no isolation capability. But most important, there is no adjustment for leveling the table to a close to level state.

My question to those who may have experience with these vintage tables.....My house is well over 100 years. Floors are anything but level. To obtain balance of the table I have used thin shims on each of the 4 corners to achieve as close to level as possible. Besides the capability of isolation, does anyone know if feet with isolation properties as well as adjustment for height available??