Many thanks for the great advice. I had decided to take a break from the projects until I found out how to proceed. I'm eager to try out your ideas. Physics comes in handy one more time... (Where were you when I was in boring physics class?) The material will be very visible and I want it to look good. I removed an ugly old 1940's metal clothes hamper from the bathroom wall of my new co-op and have framed the hole for some shelves (hence the thicker 'plexiglass'), and I'm replacing a scuffed, blurry 'plexiglass' window in the common hallway with a new piece. You've saved my projects! Thanks again. Sue