But if you are printing digital, then just need to think about how long the paper. 8", 10", 12", 14", 15", 18".
Since you'd stitched them, then work on the length can already. eg is a panorama I'd stitched to 5.3x15". I gave it to the shop and they printed it on their max paper size 10"x15".
The rest is just extra white space that you can either cut away or leave as is or write something onto. :dunno:
If your pix is sized 4.5"x14" at 200dpi, it'd come out something smaller at the 300dpi the machine prints to. And most of the machines print at 300dpi. Frontier, Gretag and Noritsu at least. Dunno about the Agfa.