@slaw
Good to see you are active here....!
VPI has a reputation for many iterations of pieces and parts and have to say, I am not sure what feet your tables came with. My TNT came with "upgraded" elephant feet. I believe they are the newer version with sorbathane cushions as opposed to the springs or bladder systems. That still says rubber of sorts in they system so I may have to go on a mission to find some Ultras...
I do really like the Mk V platter, it has been a good upgrade. I am still betting the ceramic bearing is a big improvement to go along with the platter itself.
Good luck with the shelf, I would venture to guess that it has been well thought out. I am afraid that my setup may be suffering a bit because of the cabinet I am using to support my TT as well as house electronics (other than my Lamms). It is heavy oak with 1 1/4" thick top but know some vibration is induced. Thus I have placed a 24" by 32" by 1" piece of granite slab on it for the TT to sit on. I have some absorbent material between the slab and oak but when I apply the tap test to the oak, some vibration does bleed through. A never ending quest....