We are trying to find the correct size unit for new construction of our guest house. The house is approximately 1600 sq feet under air. Two stories with only two windows on each floor. The first floor has ten foot ceilings. The second floor has 8 ft ceilings in the center for a span of about 12 feet going down to 4ft at the side walls. We would prefer to use one unit. We have been told 3.5 ton to 5 tons. Please help.