Just put tape over the red window...
But without the frame numbers on the backing paper, (showing through the window),
proper frame advancing/spacing is a bit difficult...at best.
And, without the thickness of both the film and backing paper against the pressure plate,
the film may not lay flat and firm in the film plane.

Just saying!
A few too many hoops to jump through. But, if you already own one of these cameras,
then I do understand that a few people will be happy to go the extra mile to be able to
shoot with some fresh film...much like those who cut down 120 film for 127 cameras.