For those who are interested, new pictures are at:
Rebuilt my scissor drive projector lift, as it just wasn't working. The new version rides on ball-bearing drawer rails, which you can see in the pics. I also have four "down" limit switches in parallel -- all four corners must be down before the motor circuit is interrupted.
One final thing I'm proud of is the attachment o fthe cover, using the perforated drywall corner bead. Adjusting the four springs allows for precise positioning of the cover so that it snugs up into the ceiling.
Lift and screen are on an X10 appliance module which lowers and raises them.
I'll draw up some good quality instructions and close-up photos, a few people emailed me and said they'd like to try to duplicate it.
E. Lee Dickinson Entertainment Design and Technology