Drill one 4mm hole in the center of the z-stage base plate in line of the centers of the two original cutouts. Drill two holes 3mm at 10mm left and right from the 4mm center hole. Counterbore 5mm tapped blind holes, 2mm deep in the acrylic buildplate. At rear centered, at front at +/-80mm from the center of the plate. Use the end of the laser engraved ticks to place the blind holes. The cone shaped bottom of the hole has to match exactly the tip of the supporting headless screw. Move print head to the front left and right corner and use the Ultimaker tool screw driver to adjust the platform height. Finally adjust the rear center screw.