If you ever have to replace one of your AC's, I suggest getting a 15.0 for the front and leaving a 13.5 in the back. On my coach,the factory installed two 13.5's which could not keep up with the summer heat in Nevada or Arizona.
Lucky for me, my back 13.5 went out while under warranty. I had the dealer put the front 13.5 in the back, and I paid the difference to have a 15 put in front. The difference was like night and day, and we could keep the coach comfortable during those extremely hot days.