have you been comfortable?
has shading changed?
has roof color changed?
has insulation in attic settled?
the ducts may well need sealing with mastic, especially at the branch takeoffs= probably hand made junction there --
tightening the house envelope, sealing penetrations, around doors & windows, will save $$$$$ in first costs, & thereafter energy costs.
did old unit run for hours on 7/20?
if not, it was too big!
harvest rainwater,make SHADE,R75/50/30= roof/wall/floor, use HVAC mastic,caulk all wall seams!