It seems to me, that one or several circles of cork or rubber gasket material, placed in the cap would have done the job.
The thickness would have to be determined after tightening and trying some test pieces.
I would think that it would be way less work and would not change the cap at all.
His solution is ingenious and is adjustable, but what if the cap would crack when tightening the setscrews?
Is there something I'm missing here?
It seems the problem was caused by the gasket being compressed over time and thinning. Allowing the cap to be screwed on past its original seating.