Do all color films have the manufacturer's codes along the long edge of the film? I know that's a strange question, but I was thinking of experimenting (eventually, when I get my camera) with using three sheets of 4x5 color film at once in my 5x12 holders.
I'm not sure about the consistency between manufacturing processes with respect to the edge coding (as opposed to notch codes), but I'm even more unclear about your objective of loading 3 sheets of 4x5 into a 5x12 holder. Are you thinking in terms of separating the image into three segments, individually framed? If so, I'm not sure I'd trust the film staying in position, and not overlapping as a result of being jostled during normal handling of the holder.
My Kodak C-41 sheets have the film name printed on the short edge that has the notch code.
I'm sure that I'd have to use double sided tape to hold the film in place. I was thinking of trying to get one picture from three sheets.
Even if the double-sided tape didn't distort the focus plane, Diane, I think you'll still see lines at the film junctions if you were to make a single print combining all three negs. If printed separately, however, the gap might be small enough to allow the prints to be trimmed slightly and joined.