I was talking to my installer when my new unit arrived. We unboxed the unit and I signed for it. The installer's helper was finishing up the ductwork in the basement and we were talking so I asked what was left. He said to me that he would attach the final ductwork to the side of the furnace with the air cleaner. I asked him how the air got from the air cleaner into the furnace and he said he would cut a hole in the side panel. I was like "OK, see you Tuesday." I got to thinking about it so I looked at the unit and I don't see any markings on the side of this thing that say "cut hole here" and then I looked at the manual and it there is a picture in the diagram that says cut-out but the dimensions damn sure don't match the size of my 25X20-25x10 return air boot. In fact the boot doesn't look like it's the same size as the Goodman air cleaner. I started to panic. That's when I found this site and then I read the thread by oldgoodman. I'm thinking about calling the installer up and grilling him this hole cutting business but I don't want to be an a-hole if I'm wrong. Is cutting a hole in the side panel of the unit standard practice? Am I missing some special air entry side panel? I'd rather have to get a new installer instead of a new furnace.