This can be a problem. Try to find 8x10 wooden film holders. They are a little smaller than the modern plastic ones and may fit better. Otherwise, bring out the sandpaper.
I own an antique whole-plate camera that originally was a dry plate camera. A previous owner sanded the rib off the Eastman film holders so they would fit. Camera and holders work perfectly and give me good, sharp negatives. Not bad for an 1895 camera with 1920s film holders.