Gotta be careful with stuff like this, when you sandwich plastic against artwork and it's not sealed or buffered in some way dirt will get in and the plastic will shift turning the thing meant to protect into a clear sheet of sandpaper potentially damaging what's underneath.

Actually, I tried this probably 5 years ago and abandoned it because I noticed early on that the vibration of the machine was starting to cause any piece of sand or dirt that managed to get in there to start to mar the art. The plastic doesn't need to 'move' so much, the bolts don't stop the sheet of plastic from vibrating just like blowing on a reed in an instrument.