20 foot cable? Seems excessive. My gut tells me that there is a simpler way to do what you want. How will you be demonstrating this exactly. Kids will be walking into the workshop area? Or will you be wheeling it out for them to see? Can't you use a small monitor like a //c monitor, Apple monitor or even a Commodore 1702 monitor?
Infoage wants all the groups to do some classes next year, as you know. For the classes I'd move the desk (it's on wheels) to the small event room down the hall. But I already started doing some impromptu demos when I sense that a kid is patient/smart enough to understand it and when we're not too busy with other visitors. For those demos I let the kid/parent into the workshop .... another reason for me to oblige your constant reminders to keep it clean/organized. :) The small //c monitor is no good because it's monochrome. Adam and I put the larger //c color monitor there yesterday, but a normal size color monitor = takes up valuable desk space and it won't fit on the window sill. So, our choices are to order another 2x3-ft. flat shelf (we're out of them, and they cost around $25) or to buy a $6 cable and just hook up to the huge screen on the wall. The cable will be tucked away behind stuff, not in the way of anything else, and (I think) I showed you the A/V switcher box that I already brought it. Box makes it easy to press a single button and change input sources -- one button each for the Atari, Laser, video sources, etc. ... and when we do the real demos in the classroom we'll use projector. See, I got it all figured out. :)