This is a good idea. Mine had bad seals. While there wasn't any light leakage, the back door was prone to opening when bumped. Not a happy thing mid-roll! The light-seal replacement was quick.
Originally Posted by Jon Goodman
Consider also taking the top off the camera and cleaning the rangfinder mirrors/windows. This will brighten things considerably. Also, there was a trick posted about putting a small piece of tape on the viewfinder window--in the same place as the rangefinder patch. This really helps make the rangefinder clear.