We have a 2400 sq ft house that was built in 2000. We were told by an air conditioner sales rep that our air conditioner is almost too small for our house. However, he said that if we increase the air intake by cutting another hole in the ceiling it should improve it. Meaning that on the hot 107 degree days we should be able to keep the house a comfortable 72 degrees. Is this true?

There is more to it than that. Call a real professional for a ON SITE inspection. Sales reps know little or nothing about the business. That is why they are sales reps and not service people.