A Y-shaped section of black mylar was cut on the laser cutter with some holes to attached to clips printed from PLA.  A section of copper foil tape was placed in center of the Y for contact with the nozzle.  With the probe clipped onto the printer, the copper foil hovers a few mm below the nozzle.  When it approaches the bed the mylar levels and conforms to the bed surface nice and flat while the nozzle approaches.  Minimal extra external force on the effector is an added bonus.

The slow drift was seemed to converge at a stable value over hundreds and hundreds of relative probes in the same location.  The probe speed was 1 mm/sec and the lift after contact was 1 mm as well so during the probe it just moves up and down by 1mm.  Previously the initial few probes were found to be consistent after homing the printer.  Instead of homing the printer was commanded back to near the top and back down.  Nearly same travel as home movement but without triggering or resetting stepper positions.  This process cleared the observed drift and returned back to the initial probe reading.  Smaller changes in Z height as well as just travel in X and Y also reset the drift to initial value.

The copper foil and the mylar are about 0.3 mm thick so a smidge thicker than paper 0.15mm.  A hole in the mylar for the nozzle to pass through with two layers of the foil tape on the bottom of the mylar would get this to be truly a digital paper test.  The mylar should be good for contact with heated bed, contact with heated nozzle might cause problems with plastic ooze and deformation from the heat.