I would like someone to explain to me how it is more efficient for a 13 x 24 x 21 evap coil to be more effcient than an old 22 x 24 slab coil. I understand surface area and how all of that works, but the fact is that you are taking a 22" hole and closing it down to a 13" hole. Not only does this not seem inefficient, it seems that you won't get enough air across your heat exchanger in a fossil fuel situation. I have to wonder why we did away with the slab coils when the 13 seer units came out. I think that we took a step in the wrong direction with the airflow in this senario. What do you all think?