I'm milling around a pulley system, where the cable and two pulley's are spaced two mask widths plus apart. The mask is attached to the front part of the cable that runs around the pulley's. Pull it up or down into position depending if it's the top mask or the bottom mask (being two separate systems), and turn a thumbscrew coming from the front of the pulley and cable to secure. Easily adjustable to wherever the top and bottom of the picture end up, depending on aspect and centering. Mount it all on a board, so the whole thing is just a little bit deeper than the thickness of the screen frame. Maybe put a cap over it all just for appearances. The system sits left and right of the screen, attached to the wall, and the mask extends that much beyond the screen edges.
Problem is, I'm better at thinking stuff up then implementing. And when I do implement, I screw it up a couple of times before getting it somewhat right. If I could buy this setup (Hello Carada folks!) I would, rather than going through the motions.
See ya. Dave
"High Fidelity audio has been like a dog chasing his tail. High Fidelity in my marriage has been much more rewarding because she knows where I sleep."