I did find a Stewart drop down masking arrangement, so maybe this was the one I was thinking of: It lowers down like my screen does, but then the two side masks can motor in and out. Really cool, but now is the other extreme in that it was serious
money to be thrown at the problem.
Today I tried to make the side masking by just stapling the velvet to some 1" 'stripwood' to give a sharp edge, but the staple gun made a mess of the wood and the material went all saggy.They were supposed to be like two curtains with a stiff edge nearest the screen, but just didn't work out. Maybe I was too impatient as I thought I'd have it done in no time and left it too late to go out and buy some extra wood, etc. I did get some 'cup hooks' which will screw into the underside of my screen pelmet so the masking would just hang from these hooks, using two more fixed to the top of each masking panel. It seemed really easy until I was fighting with the material and staple gun.
Instead I think I'll make the two masking panels out of flat plywood/thin MDF and wrap them with velvet which I can secure on the back somehow (maybe sandwich the velvet between the MDF and some wooden battons). With a horizontal batton across the top to give something for the cup hooks to fix into. I'll worry about making them moveable later: For now just being able to hang the two up at the start of a 1.85:1 viewing session will do for now (it looked great last night with the clothes pegged arrangement once the lights were off
However, if anyone can point me to a lower budget version of the Stewartscreen Electrimask then I'm all ears.