Weight, Clamp or stabilizer?


I have a vintage Pioneer PL-560 Direct-Drive Automatic Turntable purchased around 1980. 
https://www.vinylengine.com/library/pioneer/pl-560.shtml
I'm trying to get it to produce the best sound its capable of.  I plan to order a set of SVS subwoofer feet to replace the worn feet (I have an SVS subwoofer and removed its feet and temporarily placed them on the TT base with good results).  I read an article about TT tweaks.  A few things they suggested were an upgraded mat, clamp and isolation feet.  Thing is since the TT is a direct drive I don't know how much extra weight it can take (if any), and the spindle is about 7/8 inches tall so I don't know if that's enough for a clamp.  The original rubber mat it came with is in great shape. Do I need to replace it, too? I'm willing to invest in tweaks to improve this turntable, but not interested in replacing it.
mewsickbuff
Check out the Clearaudio / Souther Clever Clamp.  $35, hardly weighs anything and works.

The SVS feet might be good for a turntable, but they are designed for heavier devices.  I don't know if that will matter or not, but something to consider.

I recently picked up some feet from mnpctech for my JVC direct drive turntable and they were a big improvement over the stock feet.  Looks like they have them for Pioneer tables -  https://mnpctech.com/turntable-feet-replacement-isolation/pioneer-dj-plx-500-plx-1000-turntable-feet-replace/

My JVC is an 80's vintage turntable also and the rubber mat works fine.  

The best lightweight clamp with chucking lock arround the spindle is Orsonic. The silver panel on top act like a button to open chucking lock. It's cheap
For those not overly concerned about their "audiophile cred", the Orsonic was rebadged as a Monster Cable clamp. Totally identical, but for the name — and the price: ±400 for the Orsonic, ±100 for the (ugh) Monster these days. So if you'd like to save money, and can live with the ignominy of owning the Monster brand...

I had one and it is, as Chakster says, a great clamp. And it looks great: not ornate, nor a characterless block, it looks like Saarinen might have designed it.

It is not, however, lightweight. Many clamps are far lighter, and with the collet/cluch mechanism, weight doesn't matter — except to the bearing. 

I HATE stopping and starting the turntables.
Changing LPs while the platter is spinning is not ideal practice.
Thanks everyone. That’s a lot of information to process. Since my turntable is almost 40 years old there’s a chance a weight could be detrimental to its bearing so I’m going to pass. I’ve changed out all master sleeves, cleaned my records, and have an anti-static brush.
@ big_greg the Pioneer feet are very nice looking but out of stock and as mentioned earlier, I tried the SVS feet and heard a positive improvement.
@ chakster, I have the Shure m97xe high-performance magnetic phono cartridge. I’ve found it revealing when the album is. This is my 2nd. Bought a new one after wearing out the 1st because to my ears, it was worth it.
Still wondering about other opinions on the rubber mat.