Think about the geometry a minute....unless you move the pivot point of the rocker up or down, your initial contact point on the valves will always be the same when the valve is closed on a shaft mounted rocker. The length of the pushrod makes no difference on the rocker to valve contact in this type of setup.
In order to move that rocker to valve contact point when the valve is closed, you would have to shim the rocker stands. With stud mounted roller rockers that you usually find on SBC and SBF heads, you are changing the geometry of the setup by moving the pivot point up or down, hence the rocker to valve contact point changes with pushrod length.
Also, the contact point of the roller is not going to stay centered during operation. As the rocker moves thru its arc, that roller will sweep across the tip, so usually they are set up to start just outside the center of the valve and end an equal distance on the other side. Pushrod length is critical to achieving this on a SBC or SBF because the pivot point moves ans the pushrod length changes. Not so with a shaft setup.
On typical shaft-mounted adjustable rockers the adjustment is done thru screwing a plunger up or down on the pushrod side. A .019" shave should be within the adjustment limit of your rockers, but you'll have to check. A hydraulic lifter is going to preloaded by .030 to as much as .100 inches.
Anyway, the bottom line is, on a shaft mounted rocker the only things you will effect with a longer or shorter pushrod is the location of the adjustment screw in relation to lifter preload. The rocker to valve tip relationship is unchanged unless you move the shaft pivot center.