A registration device for a mail processing system having wide print nozzle arrays that reduces problems associated with printing on variable thickness media. A thin wire, held by guides, is strung across the print nozzle openings in the registration plate to support and guide the top (print) surface of a mail piece and to prevent the mail piece from protruding into the openings. The guides are positioned such that the wire passes between zones where there are no print nozzles located. A tensioning device is provided to adjust the tension of the wire to ensure the wire maintains its position within the openings. The wire acts as a guide to maintain the optimal gap between the mail piece top surface and the print nozzles.