My stock Dometic roof unit sits over the rear end and is ducted along the ceiling all the way to the bedroom. After the new one was installed, I checked the output along the duct and by the time you get to the bedroom, there is precious little air blowing out the vents. There are 10 pairs of vents (cold & return) along the duct. So, in effect, it only cools the main cabin. I considered adding another 16K roof unit, but my rig is not wired for it, and the technician did not think there was a duct housing in the rear, meaning the second unit would blow direct down into the B/R. That would have cost $1700 installed. I spent $289 for the portable 13k which sits in the closet and vents through the floor. Ideally - yes, I'd rather have the roof unit.
