I ain’t spending all this time and money and not doing it ’right’.
Or, ’supposedly right’.
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Clearance under the dust cover: presumably (always dangerous), Rega sells shims that do not cause a problem. It is possible that a larger diameter counterweight, by itself, or, if added to the shim ’lift’ will not fit.
My Mission arm has a titanium counterweight, (very heavy metal) purposely to keep the length of the counterweight section short behind the pivot, and the overall height low, both were issues when I added my 3rd arm on my plinth, it ’just fit’.
When I added a 3/8" thick spacer under my long arm from Russia, by luck (I hadn't considered it) it 'just fit' below the dust cover when on.

