A suggestion for re-installing 2 rear screws. This is the trickiest job of all. If all else fails you can always use a dab of glue or velcro to secure the 2 pieces at the back, as it is a very sturdy design and the 2 screws at the rear are probably of debatable necessity in any event, so don't be shy. You just need dexterity, patience, creativity and a small mirror.