I'm intentionally buying over-sized systems because I expect them to lose efficiency and cooling ability over the next ten years..
Redundant and oversized? There are enough safeguards in the design calcs to handle this. Oversizing will not only increase cost but also may not remove humidity as well as a right sized or even a littl undersized that will have longer run times. Remeber this is sized for the WORST CASE design conditions that are seen only hours per season
Reconsider your assumptions
You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!