I just sent this rotating circle idea to a friend who might use a 11-1/8", or a 12.16" length. The metal ring simply loosens so you can rotate the black insert to any distance, then re-tighten the metal ring.
Always keep in mind, the rear end of any tonearm moves back, and right, co-ordinate so it fits inside a dust cover. If the cover is removable, you don’t need to worry about the right side during play, just the back end when it’s parked
https://auc.aleado.com/yahoo/
I buy on Aleado, can tell you all about it, that, buy it now $177, add fees and shipping to usa, I guess might total $250. On the right side, there is a ’destination’ box, with a pop-down, you pick your country, they estimate a total for you, add some to that.
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This listing shows a mounting plate with an oval cutout. Seller is keeping it.

