I have tried to track down a 5" hole saw to make cutouts for 120mm fans. The closest that I have been able to find is a 4.5" hole saw. Is this what you guys use? Would that work? I have found this ...

Diablo’s Demo Demon Carbide Teeth Rough-in Hole Saw range is available in various sizes from 1-3/8 to 4-5/8 in. and one, eight-piece set.