Our 5er is set up for a 2nd AC unit up front including a 50 amp service and dedicated 20 circuit with 12 ga wire in the ceiling near the front ceiling vent. I'm thinking about installing the 2nd unit ...
Check e-bay. I did this last year. A Dometic Brisk Air 2, 13,500BTU non ducted with ceiling assembly. Now $484.00 with free shipping. Easy install. The hardest part was removing all the goop & sealant from the existing bedroom vent. Measure to see if the unit will work for height. Keep it under 13'6".