Is this correct? My HVAC contractor agreed that our house only needed a 3 ton unit (3150sf, SIP walls and roof, energy efficient everything.) However, he says we have to have a 4 ton unit in order to match the blower necessary for the size of the house. Is this correct? He says it doesn't matter if the unit is oversized since we have a Carrier Infinity 19 and it will only run on low unless really needed. Now that it is installed, I have never seen the unit run more than 6 minutes even on a hot day. I am not sure if I can tell the difference by hearing but I cannot say the unit has ever sounded like it was running on 2 different speeds.