Once I get around to cleaning the camera, I plan to do that. I've also heard about the rangefinder modification. I'll probably give it a try just to see if it helps me or not. The rangefinder patch looks pretty good in regular indoor light.
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.