Have you tried taping them to the tympan? It would be crazy slow going, but it would keep your register. Say, use a few squares of something like this (http://www.staples.com/Scotch-Restickable-Strips-1-inch-x-3-Clear-6-Pack/product_857700) on the tympan–making sure that they’re not under an area that’s being printed, and also that the area would be hidden when you fold the sleeves.