I know this has been discussed many many times, but figured I'd try again with recent work done. We recently changed out an undersized AC return in our stove room. It's a 12" duct but for whatever reason had been reduced to an 8" grille. Our house is not an open concept at all so our stove room gets blazing at times. After replacing the grille (old size was 8x14, new is 14x20) I wanted to try again since more air should be getting pulled with the newly sized return. I turned the HVAC fan on- at the return it's just over 80*- at the far end of the house air coming out of vents is 72-74, with it being mid 30s out. Even though the air coming out is nowhere near what it would be with the heat on, rooms that typically stay cool while running the stove were much warmer. I suppose the true test will be when temps drop to the 20s however I'm pretty happy with the results thus far.