Steve...

A little problem with two sheets of glass is the light hitting the baseboard and reflecting back onto the target paper... I would modify that and use a piece of black plexiglass for the backing board and then some plate glass (available as scrap size at 11x14 from most glass shops, but be sure to have the edges sanded so you don't inadvertently add unwanted red color to the print). This set up will only need the tape replacement as it wears out from repeated use. Be sure to tape both inside and outside to allow for the thickness of the materials being placed in the "sandwich".. lettuce excluded.