This is my first post with this forum. Let's see how it goes. I am a general contractor installing a new roof on my clients house. While inspecting existing framing and sheathing in the attic like I always do... I noticed one rafter missing. There is a framed out flu pipe in the center of the bay near the ridge. Someone attempted to add 32 inch cats every six feet or so. I would like to add more cats instead of demoing existing cats and adding two twenty foot rafters which is never fun doing as an after thought. My question is if I add a cat every 16 inches... Would that be equal to having a rafter installed. Is it to over kill? Maybe every four feet. There is no live load and the roof sheathing is half inch.