SOTA NOVA, HR-X VPI, Technics 1200G recommendations?

I have had two Sota Turntables over the span of 39 years. My latest is a Star Vacuum Series VI. It was a series V until the motor died. So I had them upgrade it. The speed is stable in terms of both setpoint and w&f. My older Sota Sapphire Series III with the Pabst DC motor had speed variation and I ended up modifying the suspension to reduce w&f which made it sound much better but it would still have a different set point every time I turned it off and back on.
The Series VI is an A/C motor vs. the Eclipse being DC. I thought about going with the Eclipse but decided to keep cost down and also minimize the modifications. I’m very happy with my choice.
But regarding the excellent isolation properties of the Sota turntables. Over these many years I discovered that the Sota turntable can still benefit from additional isolation. I wanted to share that. I also have tried using the points (or Cones) on the three legs but I went back to the rubber feet. I prefer the sound with the rubber feet. My new favorite isolation configuration is a carbon fiber plate on 4 ISO Acoustics feet. Wood boards work well too. Do NOT put the Sota on a granite slab. I thought that would have been a good thing for the extra mass, but the sound is terrible.
The vacuum improves bass response and also makes the background blacker- at least I think so. But I also like the vacuum because I have a few records that are not perfectly flat and while the clamp alone helps the vacuum platter makes every record perfectly flat.

I want to clarify things about Technics SP-10 mkII:

-You don’t need that old and fragile obsidian plinth at all, you can make a bigger custom plinth with many blank armboards for whatever tonearm (including 12 inch) with any diameter of the mounting hole. 

-AT pneumatic insulators under the plinth is a must and you don't need any isolation platforms, just a good rack.

-Great alternative to CU-180 and CU-500 is lightweight mat SAEC SS-300


p.s. All pictures above made by myself, it’s my ex Technics and stuff.

I'm running SL1200G with Ortofon Bronze, could not be more happy!! 

I've got an SL1200G with a Clearaudio Charisma MM cartridge, going into Herron Audio phono stage and line stage preamps. Sound is AWESOME...

@lewm, I promise I will not come back at you with airborne vibration 🤐
Exactly, I did not buy the Infinity arm because it was not stiff enough. I got a Syrinx PU 3 which was not a neutral balance arm but it was very stiff and no removable head shell. The removable head shell and it's socket are unnecessary mass at the end of the arm and an additional set of contacts. Maybe it is only a few grams, still IMHO unnecessary. Although the SME style locking mechanism is very stiff you are probably right, a fixed head shell is stiffer. The arm tube on my Schroder is dampened carbon fiber BTW. 
A stable balance tonearm increases VTF as it goes up. That is why it hunts for the balance point. The easiest way to tell is lift up the arm just an inch and gently let it go. A neutral balance arm will just stay there. A stable balance arm will start hunting up and down. It is not enough to have the counter balance weight at the level of the record. The center of masses at both ends of the arm have to be in line with the axis of the vertical bearing. I have played with a FR arm. I do not recall the model.
There is a lot you can tell about an arm by just looking at it. For instance an "S" tube arm is going to be heavier than the same arm with a straight tube. The straight arm will also be stiffer.  An arm with a removable head shell is going to have more mass than the same arm with a fixed head shell. The Kuzma is a great compromise BTW. Mass at either end of the tonearm is more significant than mass near the pivot. This is what effective mass is all about. Like a seesaw inertia is affected most b mass at the ends. Inertia is different than effective mass. 
Tonearm design requires a bunch of tradeoffs. Is there one right balance?
I doubt it. I prefer lighter arms and more compliant cartridges but there are limits as too how light you can go. Is the FR stiffer than say my Schroder. I seriously doubt it. IMHO the FR does not justify the added mass. For stiff cartridges I would rather add just as much mass as  needed to the Schroder.