what i call "swedge" the locknut? ok.. you install the feeler gauge.. got it where you want it. you turn the outer locknut and then tighten the inner allen OR do you tighten the inner allen just before you get the locknut where you want it and tighten them TOGETHER... i always have done it the latter way on other makes of engines but a buddy of mine told me reher morrison (local to us) said NO NO NO.. set the locknut, tighten the inner allen and install your chebble stud girdle! that doesnt apply to us though... so whats your procedure..? maybe someday after obamas gone ill get my rockers back from RAS and i can adjust valves!!! lol

One of the real fast Mopar old time racers told me to make sure when setting the lash to make the feeler gauge was real tight to push in after setting the valves, real tight. I set the lash and add around 1/10 to maybe 1/15 additional turn before tightening the locknut, tighten and check the lash, adjust as needed on the tightening and adjusting When the feeler gauge drags out hard I know I'm close

Insert the feeler gauge and snug down the adjuster. Snug down the nut. Now torque the nut. The change in clearance is negligible. I don't try to hold the adjuster while tightening the nut - besides, I use a socket.

my crane rockers are 9/16 size socket lock nut and a allen adjuster
i make mine a tad tight and on mine it gets looser when the lock nut binds the threads.
i cut a deep socket and welded it to a piece of flat stock steel
drilled a hole for a "t"handle allen and easy as pie. it was a eye opener finding out i needed to go 5thou tight when doing it cold though.

get yourself a set of go-no go feeler gauges, imho it's the only way to adjust lash 2¢