Some of my rocker pads are worn on Vitesse. I worked out using feeler, that 10 thou " related to about 60 degrees of adjustment turn on screw (another member calculated by the thread pitch, it should be 90 degrees/quarter of a turn, though this worked out too big a gap for me).
So I closed up the gap finger tight and backed off 60 degrees (or 10 minutes of a clock face, say) turn of screw.
Tappets quieter, though still some noise when accelerating until engine gets hot. Fairly quite at idle (could this be rocker/shaft wear, if more noisy on the go?), which is why I found it hard to use the feeler whilst engine running technique.
Not sure if this way is ok really, though should work in theory?.
Cheers, Dave