I have a customer who needed a backlit sign for a indoor drink machine. The sign is 9x30, I had it printed on .10 polycarbonate by signs365(their backlit media). Problem is it's too thin to install by itself. I have a piece of clear polycarbonate I want to attach the printed to. Any recommendations on attaching it? Will spray glue work or will it show when lit? The printed Poly has a full printed distressed grey background, it's not plane white if that makes a difference. Any help is appreciated.