...Mr Gunson says to put a 10 thou in first, set the Gunson & then ADD another 10 thou on top !!....How's that work ?? .....I think the traditional method is the best way forward........don't reinvent the wheel !!
Instead of the Clickadjust (sp?), you could set the clearances by using two feeler blades and allow for the wear ridge that way.
You know what the correct gap is, yes? One blade alone won't read that gap accurately as the rocker pads will have some wear on their faces so: Enter the correct blade plus another (size unimportant but I tend to use a thicker one) then count how many turns are required to reduce the gap by the thickness of the blade which equates to that gap.
Then remove both blades and screw down the adjuster until there's no clearance at all.
Then turn the adjuster up by the number of turns you measured earlier, that will give you the exact clearance required but will allow for the wear step that, were you to use just the one blade, would cause the actual clearance to be too tight to enter the gauge.
The above is exactly how the Clickadjust and other tools of its type will work, but obviously the device is quicker than the two feeler blade method and even more accurate as the gearing within the device means that your gap can be tied to one tiny movement of less than a minute rather than the few degrees you'd see when going to retighten the locknut when you've counted the turns manually.
So nobody tried to reinvent the wheel, the Clickadjust works, reduces the time required to do the job with two feeler blades and gives greater accuracy.