Hi Bert,
I'm planning to attempt to make a screen that can be used for 16:9 and 2.37:1, and possibly 2.35:1 as well. The screen is going on the wall in my loft, which of course is wider at the bottom than the top due to the sloping roof, so I'm going to make the screen the same shape and mask it as required. The idea being I can have a 10' wide scope screen for movies and an 8' wide 16:9 for the football.
My limited DIY skills might force me to settle on a basic rectangular scope screen, but the slope of the roof will accommodate a higher (but narrower) screen so I'm going to give it a go. It's an extra foot or so of viewing area across the screen so I think it's worth trying.
I'm planning on using black velvet fabric, stuck around wooden batons at the top and bottom of the screen. The sides and top for the scope screen will be the same velvet, but with an edge overlapped around that plastic coated wound wire you can screw hooks and eyes into the ends of. I'll fix batons around the screen to hook the masking 'curtains' on to. I'm hoping the wire will be taut enough to give a nice straight edge, but without creating shadows.
I think the top mask for the scope screen might be a problem, as it'll be shaped like a roof and at 10' wide it might be difficult to get a taut edge. And of course I'll need to remove it when I want the 16:9.
The key is whether the wire is taut enough to give a crisp edge, I'll find out I suppose