Outstanding, Maurice! Thank you. A lot of this I'd already worked out through trial and error, but some bits completely took me by surprise.
I had a film professor at a local college criticize my use of a magenta backlight as "amateurish", but he had no answer to my request for a better color to neutralize bounce from the green screen. Perhaps I simply laid it on too strong.
Which leads me to my next question ... what do you suggest we use for a green screen? I have a simple, folded sheet of green fabric. When needed, I unfold it, steam out the wrinkles, and [try to] tack it up smoothly. I use a fluorescent light fixture at the floor level to illuminate it, then a magenta backlight on the talent. The trouble with this is that the sheet isn't very wide, so when I have talent far enough in front to avoid spilling shadows on the screen, they have to minimize their movement or they wander off the sides. I'd like to have something big, easily lit, easily transported, and easily stored ... preferably eliminating the steam-before-use step.
Your tips have made this the most interesting thread on TrekBBS ... thanks again!