According to an article by Bob Thomas that appeared in the Anniston Star on July 7, 1958, Howard Hawks and John Wayne toyed with the idea of shooting Rio Bravo (1959) in the three-camera, 2.59:1 Cinemiracle process.
Hawks: “I think the time is ripe for putting a story on that big screen. Wayne and I have a story which I think would work — a kind of a Western… It won’t be easy. You’ve got to have a very special kind of story for the big screen; one that gives you a variety of backgrounds.”
I’m guessing the story of Rio Bravo changed a bit, since the finished film doesn’t boast a “variety of backgrounds” — just the sheriff’s office, a couple saloons, the hotel and a couple spots in Old Tucson.