I think your hitch height (with 15" wheels/tires) is 17 3/4" according to Airstream's specs. Most hitches I have seen recommend setting the top of ball height about 1" higher than the hitch height.
That should be correct. Maybe someone else can second my information, but that was the published height to the top of the coupler for a 2015. I do not believe it has changed for 2016.
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