Like Rick, I was in the sign business for almost 39 years. The info about polycarbonite (i.e. "Lexan") is spot-on if you are concerned about potential vandalism or high wind debris protection, but is very expensive initially. Your better grades of acrylic and Plexi will contain more UV protection properties, but again will cost more. The only way I know of to use thinner materials and resist wind blow-out is to install a back grid of wire or mesh to reinforce the face; this, of course, will not work if the sign is backlit. I might suggest, if your sign frame position is low enough and close enough to your viewer's street vantage point, to use reflective vinyl lettering on a stabilized wood or anodized aluminum sign face. These substrates are not cheap, but IMHO, comparable to high-grade plastics. The advantage is that these faces are more impact resistant, last longer, and the retro-reflective lettering will utilize other light sources, such as oncoming vehicle headlights, to "punch" out the copy for legibility without depending on an internal light source. I apologize for the length of this message, just thought it might be another way.
then was offended when I laughed.
