I had a new central AC system installed about a year and a half ago, and I am wondering if what they did is allowed. The plenum on top of the furnace/A-coil needed to be slightly larger to fit the size of the new system, so the installer enlarged the plenum by building it around one of the rafters that was directly above the furnace. So now the rafter goes right through the plenum. It seems to be sealed well around the rafter. I'm sure that this isn't recommended, but is this allowed by code, and will it cause any problems down the road? I don't think that I want the installer touching anything else at this point, so I will do any changes necessary, but if it will be "OK", while not good practice, I'll leave it alone.Thanks.