We have the 29M with 2 ac units and the enclosed heated tanks. I would say that if you plan to camp anywhere hot (like Florida), you need both units.
Before buying our Windsport, we lived 10 months in a travel trailer (selling our house!) in Florida. The unit only had 1 ac and it cooled fine but the ceilings were much lower, way less windows, and it was 3 feet shorter than our Windsport.
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