That's the most accurate method, since the collapse distance of a hydraulic will differ slightly between manufacturers.
If you have to remove any metal from the rocker itself, obviously take as little as possible but blend the cut into the body along the edge in both directions to "fade out".
BTW: the H-S are extrusions to keep the price down, and could be profile milled to save some weight if you know where, especially on the roller side. Don't reduce the height, but the width can be sculptured a bit with little bas-reliefs.
I think of adjuster motion in terms of hex flats on the head or wrench, 7/16-20 NF is 8.3 thousandths per flat, 3/8-24 is 7.
