Both projectors will be on the same HDMI cable. A blank powerpoint screen would blank both projectors. As of now, we plan to always send the same image to both projectors. This is part of the "keep it simple..." objective. It will depend on the activity if we use the front, back or both.Would it be possible (and easier IMO) to just add a blank slide (assuming Keynote/Powerpoint) that is black and then have the screen go away? That's what I would do, instead of trying to control them independently.