Hi Chris, I think the decoupling offered by the wood plate is a very drastic solution, applied in desperate situations. My concern is about the strength & tightness of the surface that couples the arm pillar with the arm pod.
I'm sure it works OK, but from the theoritical point of view, I would be more comfortable if you choose a more solid upper fixed point, in order to modify the ET arm pillar, as if it is one piece with the first block of the arm pod. Even if it is applied at the bottom* (the decoupling by wood), may not be necessary -in your case- considering there is a film of air in between the arm tube & the arm pillar.
* Steel at the top plate, your own Al main block, Brass as a foundation or intermediate level. Especially the discs that rests the spikes must have great hardness. You can close the microscopic open moleculars between the metal surfaces simply by applying some silicone oil without bonding or bolts. Easy if you uplevel your main wood shelf with a second & preferably denser platform only for the TT and so, you will have the apparent hight for steel, brass & discs. Just a thought.
I'm sure it works OK, but from the theoritical point of view, I would be more comfortable if you choose a more solid upper fixed point, in order to modify the ET arm pillar, as if it is one piece with the first block of the arm pod. Even if it is applied at the bottom* (the decoupling by wood), may not be necessary -in your case- considering there is a film of air in between the arm tube & the arm pillar.
* Steel at the top plate, your own Al main block, Brass as a foundation or intermediate level. Especially the discs that rests the spikes must have great hardness. You can close the microscopic open moleculars between the metal surfaces simply by applying some silicone oil without bonding or bolts. Easy if you uplevel your main wood shelf with a second & preferably denser platform only for the TT and so, you will have the apparent hight for steel, brass & discs. Just a thought.