I have one large return at the top of the stairs for the second floor and another one on the first floor. We really would like to avoid leaving the doors open. That really negates the idea of having doors in your house. I'll give it a try to test it out. If that makes the improvement, then I need to consider how to improve air flow from the bedrooms with the doors closed. Perhaps add some wall vents to allow more air flow. As it is now, you can feel a strong breeze from the air being drawn underneath of the doors. The upstairs return is at the top of the stairs and is in the center of the hall way. Would it be better to add more returns, perhaps one at each end of the hall rather than one large one at the top of the stairs?