I am drawing up plans for a 7x17 camera and I want to make my own holders too. Used ones are proving impossible to get. These have never been on Ebay when I am. If it is not too much trouble would someone please give me the Over All dimensions, and the dimensions of the film opening. I have no idea what the real name is. I would also need the distance from the inside edge of the rib to the film opening and width of the rib. Thank you very much in advance.