One quick question about return air. Would it help to take return air off the floor or ceiling. Most of my return ducts are high with 1 large one closer to the floor. Was thinking about downsizing the larger one(about 16" x 10") thats about a foot off the floor. I know this will help for summer a/c, but what about winter heat? The new size would be about 16" x 4"(or 3 or 5 or whatever).