Some more questions I have:
1. How should I center the pipe on flang on the plexiglass, with respect to the entire plexiglass or the 4 machine screws?
2. I don't think I'll be using the compression springs as I can't find the right size and the finishing washers. So without the compression spring, is this correct for what goes on the machine screw in order from top to bottom: wing nut, flat washer, plexiglass, flat washer, hex nut, middle of machine screw, hex nut, flat washer, projector. Is that right? I bought some lock washers, will I still need them without the springs, and if so, where would they go?
3. I'm having trouble detecting the ceiling joists with the stud detector I bought, a Zircon Pro SL that scans 1 and 1/2" thick. It seems to be detecting a joist almost everywhere on the ceiling, and I'm having a hard to knowing where a joist is. Any tips? I'm tried it on a wall and it works fine.