Sorry if my question is repetitive. I did try to use the search function first. I have a Kamera Werkstetten D21 plate camera and want to convert it from glass to film. I have found 2.25" X 3.25" Kodak film sheaths but it appears to me that the sheaths should be 2.5" X 3.5". Is this a difference in European specs from US specs? Would the 2.25" X 3.25" sheaths work? I find sizes are always confusing with these cameras. Thanks!