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

That’s the advice you get from ’amateurs’....🤪
HERE is the ’reality’ from Mark Doehmann, responsible for the designs of the Continuum Caliburn and Criterion turntables as well as his own Doehmann Helix 1 and Helix 2 turntables.....all of which are carefully designed with the tonearm mounting bases ISOLATED from the bearing and plinth 👍

Sorry Halcro, you fail to understand that both can be true.

Here is the brief from Dohmann...

The new ’table retains a somewhat simplified version of the unique "floating" armboard technology originally found in Mark Döhmann’s earlier designs, which physically isolates the board while maintaining (it is claimed) positional stability.

So Dohmann claims to provide BOTH isolation AND postitional stability.
I have not personally deconstructed the Dohmann but I understand that it uses a series of interlocking plates and composite materials to provide both isolation and maintain positional stability of the arm relative to the platter.

We are after all trying to measure a micro groove with the stylus - the stylus mounted on the armboard, the groove is mounted on the platter.
Any lack of rigidity between the platter and armboard will result in inaccurate measurment of the record groove. Its that simple.

If you want to perform an experiment - try measuring the height of your house whilst bouncing on a trampoline - you could post a video on you tube with and without the trampoline and we can then give you some feedback.

Sorry Halcro, you fail to understand that both can be true.

Duuuh.....🤪
You surely don't imagine for a second @dover that I could be advocating for an armboard to be 'moving' in relation to the platter....?
As you rightly surmise....

Dohmann claims to provide BOTH isolation AND positional stability.

But what he emphasises is the importance of 'isolating' the tonearm from the both the BEARING and MOTOR.
As @lewm states above...

A very heavy outboard arm pod that sits on the same support structure as the plinth itself is probably an acceptable compromise as far as coupling.

What irks me mostly is the declaration of FAKE facts....

Here is the engineering principle that MUST be observed when designing a plinth for a turntable:
The plinth must be as rigid and as acoustically dead (damped) as possible. The mounting of the platter bearing in the plinth will be thus coupled as rigidly as possible to the mounting of the tonearm.

Such dogma is anathema to our intriguing and not fully-understood hobby....🤗

There is an interesting conundrum at play here.
I quoted Einstein quite deliberately.
”Does the Station stop at this Train?

Looking at this another way, if the Station and Train are rigidly coupled together AND moving. A passenger in the train looking at the station will observe no movement.  
The challenge for the TT designer is to keep the relative positions of the platter and arm board constant under dynamic conditions. Does it matter if they are moving about provided they are rigidly coupled.? Obviously yes if this movement is large or violent because the acceleration will impact the arm and cartridge. But what happens if the movement is small and benign? 
Keeping the two parts still relative to each other isn’t easy. There is a YouTube video posted by Peter of Soundsmith where he quotes an Ortofon engineer who states that movement of 0.005 micron can be traced by a cartridge.
This tiny amount is almost beyond comprehension.

By the way, smart guys (Atma-sphere, Richard, and Mark) can differ in opinion, which does not make the persons on the other side of the argument "amateurs".

Please don't ask me to explain the difference between 'Professional' and 'Amateur' in relation to turntables @lewm ......🧐

Keeping the two parts still relative to each other isn’t easy.

Perhaps not.......
But certainly not impossible 🤗