You will find that 4x5 film is actually a tiny bit narrower than 4".
That's right. Glass plates were 4" wide, then when film took over, metal holders were made to use the film in glass plate holders. These required that the film was slightly smaller than the glass plate size.
"People who say things won't work are a dime a dozen. People who figure out how to make things work are worth a fortune" - Dave Rat.