During the heat of the day (up to and beyond 100 degrees F) I run both front and back 13,500 BTU acnds. I put a 9" fan on the floor of the bath right by the bedroom and aim it straight ahead. I put another on the floor in the front of the coach and aim it high (45 degree angle) towards the rear. If I don't get too far behind it will keep the coach very comfortable. At night I raise the bedroom thermostat 3 degrees higher than the front and usually the back unit does not run or when it does it is infrequent. I believe one needs to move the air in a coach with ducted supply and return air in the ceiling. Otherwise I am convinced it short cycles-out the supply and right into the return.