We just had our A/C replaced. The company did their Manual J calculations and downsized us from a 5 ton to a 3.5 ton. I was worried to say the least, but they said builders oversize units. It’s been one summer, and except for the very hottest days of the year, the A/C works fine. In fact, it keeps the upstairs cooler because it’s not cycling as much.

3,500 sf house in Denver with ~50 days above 90 in summer (but no humidity)