I carry a Kodak Readyload, and a Fuji Quickload, holder; the idea being that one will serve as a back-up for the other. However, if you only use Fuji Quickload films, you probably want the second holder to be a Quickload system. There are also many people who hae experienced some troubles (jambs) using one film system in the holder of the other company, so perhaps consider it a last resort.
As others mentioned, the Polaroid 545 holder is an alternative. It is larger and heavier than either the Fuji or Kodak holders. As a third back-up, consider getting a roll film holder, though that would be a smaller cropped view.
Ciao!
Gordon Moat
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