At left is a flat screen that was erected in front of the Cinerama screen and you can see the supports going right through the Cinerama screen.
I think the flat screen was put up when it became a porn house.
Strip alignment plates This murky photo is a closeup of the special plates that hold each strip just so, facing the projector. In this case we are looking at an area at the extreme left side of the screen, at the bottom. The strips are gone from the left but still in place on the right. You can just barely see how the slots in the plate hold each strip in alignment. The strips are held under tension from below but the plate is the final point of contact on the way up (or down in the case of the upper support). Sorry about the poor focus but this was taken in near total darkness with a flashlight.