Thanks for all of the input. Unfortunately, It’s not as simple as buying a weight or clamp. My spindle has a pop up plastic collar around it that drops down when an album is on the platter, leaving only the metal center of spindle above the label. It is less than half the diameter of a normal spindle, and very short. Without a record on the platter to hold the collar down, the platter will not turn. (Cartridge safety feature). The platter and tone arm assembly are suspended from the underside of the plinth by three springs, now 30 something years old, and the recessed platter surface is only barely above flush with the plinth. A 200 gram LP plus 300 grams and the platter IS flush (I checked) with the plinth as the springs stretch, and the very outer edge of of the album can make contact with the plinth. That’s why I was looking for and trying to find something light other than the clamps I see to damp vibrations on the vinyl. I’ll try the sorbothane and let you know if it makes any noticeable difference. I’m using a SoundSmith SMMC 1 cartridge.
Steve
Steve