Victor UA-7082 Arm OR Micro Seiki MA505L ...? (both fit my existing alternate 270mm hole)

Elliot, That is a very kind offer, but please don't go to the trouble. I have a big bag of faucet washers, many of which have a promising profile, and I can find one that works by trial and error and thanks to the dimensions that you posted. I've got an excellent metric caliper that will help too.  Keeps my mind off you know who(m).

The DV505 VTA adjuster is not so great compared to that offered by many modern tonearms, but it is light years ahead of the family of tonearms that place an actual grub screw at the base of the pillar with no gearing to keep the arm stable while you move it (by hand) up and down.  The DV505 at least has a gear built in to move the pivot up and down in small increments, and it's relatively easy to secure the adjustment once you are satisfied.

For anyone with an older "primitive" arm such as lewm just described, here’s a trick I read years ago for adjusting VTA.

If there is space, use a deck of playing cards to secure the height of the arm before releasing the grub screw. Then add or remove cards as necessary to adjust to the desired height, then tighten the grub screw.

Not recommended "on the fly".

Disappointedly, my early model Blackbird Arm post is not as tight a fit in it’s arm base tube as Thorens or SME precision. I had NewArtVinyl add a 2nd allen head set screw (current production change along with the 5 pin din connector so you don’t need to terminate the silk covered Litz wires yourself like I did),

I need to loosen two set screws, adjust the height up/dn, tighten two set screws; definitely not ’on the fly’. but their micrometer method provides for ’precise’ up/dn

you put something between the plinth and the micrometer’s tip so the arm stays where it is when it’s set screws are loose, then turn the micrometer for up or dn: not easier, but more precise than any arm I have adjusted. You can record the micrometer’s settings if you want to recover prior determined positioning.