Well, we've had 86° temps up here in Michigan and the one 15K unit(on our trailer) has kept the trailer cool, even in the full sun.
You may want to check the duct work and be sure that the flexible duct is NOT crushed during manufacturing. There have been reports of Keystone having some problems with the duct work squeezed almost flat in the roof area.
Also the Dometic Air Conditioner (on the 2014 models) has a slide on the A.C. itself that allows most of the cold air to be directed into the kitchen area. Of course it's much noisier using that feature but you do get a lot more cold air directed there.
A 13,500 BTU in the bedroom should be able to freeze you out. It's such a small room to start with.
Good luck,
