A brief update. I've been very occupied with other things but recently I have found time to set up the mirror screw as a permanent installation in the workshop. If you're ever in the Evesham UK area, you're welcome to a demo! (120-line colour)
The two illustrations show the screw itself, and (looking in the other direction) the control arrangements, RGB lines-of-light, and the 'hot seat' where you need to sit for the best view.
Steve O