Doing any sort of running adjustment is less than effective, but trying it on hydraulics can be particularly frustrating. Getting slapped by the cam lobe several times a second means that the lifter never gets the chance to top itself out fully, so the adjustment is always a SWAG. Engine stopped is the way to go, solid or hydraulic!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!