Planning a pepper's ghost this year... so shopping for 4'x8' sheets of plexiglass Anyone happen to know what thickness will NOT warp/bend from it's own weight if stood up lengthwise (8 feet tall) WITHOUT a frame. Planning on setting it on the ground and drilling two holes at the top corners and...

For illusions like Pepper's Ghost and the bottomless pit, I need something like plexiglass. Plexiglass is pretty expensive though. I see that Wal-mart has relatively cheap poster frames that have thin plexiglass or plastic that I could use. It occurs to me that if the whole frame costs $10...