Tonearm mount to the plinth vs arm board vs rotating arm board vs isolated tower

Dear Lew, You made me again speechless. Heavy paint? 

There are anti-vibration extensional compounds that are applied similar to paint.

Once you isolate the turntable all that damping stuff is passé. The isolation is a two way system. 🔛

Dear @atmasphere  : You are rigth and I know it because I used and use somerthing similar in my big loudspeakers. This is what you can read in my Agon virtual system:

"""  LOUDSPEAKERS.

ADS L 2030: This is a Full Range Professional Monitor that I own for many years.

These L 2030 was designed by Mike Kelly ( Aerial speakers ) and till today it match all my priorities.

It is " heavy " tweaked to do that: first it has " three hands " ( internally ) of a insulation/antivibrational treatment ( like a white paint. I can't remember the ingredients. ) from Acoustical Magic Company ( it works marvelous ) inside all the box ( a big one box: 58-5/8" ( H ) x 27-1/4" (W) x 13-1/8" (D) ).   """#


Well, I use it too in the Denon/Technics platters and Denon's metal chasis.

Regards and enjouy the MUSIC NOT DISTORTIONS,
R.

nandric, fo.Q tape is a piezoelectric vibration damping tape that works great on turntables, tone arms, and speakers. Very effective. 

Regarding platter mass, and materials, the differences are obvious and easy to hear. My Miller Carbon turntable is based on the Teres Audio platter and bearing. https://systems.audiogon.com/systems/8367 The design of this table allows the platter to be lifted off and swapped out very easily. 

Designer Chris Brady made four different platters, all identical except for construction and materials. The platters were solid acrylic, acrylic with lead shot, a solid synthetic material, and lead shot loaded Cocobolo. Chris did a demo playing the same music on each of the four platters. It was easy- and impressive- to hear the improvement from each to the next. 

Platter mass definitely does improve dynamics, drive, and bass extension and slam. Going to a stiffer more highly damped material is even better. Each and every one of these changes affects the sound. 

Try the tape. Its cheap. You'll be surprised how well it works.