Scroll to #18 YC1 picturesI found my duct system very restrictive and modified my AC covers. I still get air flow out of the ducts but this method reduced the duct pressure in the front which allows the rear AC to move more air towards the front without such a head on collision with the front air. I also found my round registers were very long and went so far into the ducts that they reduced air flow. I cut them down for some improvement.
I have to admit that after 5 years I just learned my fans are actually three speed. Someone suggested using the high speed setting versus the Auto setting. Makes quite a difference. The Fans do not shut off but the compressors can cycle and any remaining coolness in the exchangers is not sacrificed by shutting the fans off.
Currently we only have 30 amp and with the bedroom closed we were able to stay very comfortable yesterday in 101 degrees with one AC.
I also went to the roof, removed the covers, and found a couple of places where air could bypass the exchanger. They work better now than I can ever remember with the mods and maintenance.