Annie, I've gotten to the party way late as usual but for future use here's how I would approach it. The old 711 holders are loosy goosy enough I think. I'd slide a piece of 5X7 film to the end. Maybe B/W. Then I'd slide a piece of 5X7 Velvia in and overlap the first sheet by an inch+. Now there's an equal 1/3 of the first piece. Then I'd cut my final piece (B&W paper??) to the dimension of the first and second piece and slide it in to overlap the middle piece. 3 different substrates will then be in position with equal 1/3rds of the full 711 when a single darkslide is pulled to make an un-interupted triptych (sic?) on all three pieces of material. The difficulty might be getting 3 pieces that will all "see" the same exposure correctly. PanX and Velvia are about the same speed but b/w paper is VERY slow. Confused??