Haven't tried one, but be very careful about your calculations of needed 12V power. Their "recommended batteries" of two Group 31's is a joke.
2 x 110AH = 220AH total
Of this total, only 50% maximum is really available (110AH) because you don't want to discharge your batteries below about 50%.
On Medium power their 6,000BTU unit draws 35A. Thus in only 3 hours at 35A it would deplete the available power. Running it overnite....even if you really could use low power
or 18A....would draw about 150AH, plus whatever it took originally to cool down the cabin
On a hot day/night with the unit running at high power (about 50A) you'd draw down a lot of power.
And, remember, you've got to somehow replenish that energy in the house batteries.
I'm not saying it's not do-able, and in some cases it might even be a good idea, but beware of the real power required for cooling