I have a 4 level split (including the basement). On the two story living area side there there is a 25x19 air return in the hall at the top of the wall on the top floor and on the bottom story living area there is a full louvered door leading to the basement. On the one story side (which is over the basement) there is another 25x19 at the top of the wall in the dining room. The one story area is 20 ft x 24 ft with an open floor plan with only a small bearing wall (where the air return resides). I would like to reduce the size of the air return and/or move it to the bottom of the wall. I have spoken with a couple of contractors who are bidding on other work about my ideas and one says move it but don't reduce the size and the other says I can both reduce the size and move it. Who is correct?