I live is southwest Arizona so I know heat. I have re-taped the ducts up top and removed the vent shrouds in an attempt to cool the unit better. The problem with these things in there are to many cubic feet, not that great of insulation and not enough air conditioners. On a 105 degrees day I am doing good to keep main living area at 83 degrees. The bedroom is not a problem and the garage is better than the main living area.
What does make a world of difference are a couple or more strategically placed FANS.