When you change the size of object you're printing on, or change pen brand, you usually need to re-adjust the proximal arm height. You do this in order to make the distal arm horizontal when the pen is resting on the egg.
After gluing a scale to the edge of the proximal arm, as show below, write down the setting for each object for future reference. A regular Avery adhesive label seems to have enough stickum to stay in place. Time will tell.
And eyeball the setting using any straight object (pencil, ruler, etc.) resting on the two side frame tops.