JP, it may be too late to do you any good, but I'll post it, anyway. Use a slide projector with a zoom lens, and set is as far behind the actors as possible. The actors should stand close to the screen, almost touching it for realistic scale and sharp silhouetting. Use an empty slide mount in the projector for clean light. (The slide mount masks out the imperfections of the lamp and condenser lens.) Use the zoom lens to concentrate the light onto the screen for optimum brightness. You may use colored gels in slide mounts, or color slides of backgrounds, walls, clouds etc, and project them in or out of focus for special effect. You may also plug the projector in one of your dimmer circuits and control it from the light board.