I have the 15K on my 21SSL. We usually run only one bunk open, but occasionally run with both. The A/C keeps the body of the camper very cool on even the hottest days, but the bunk ends can get warm in the direct sunlight. The canvas will get hot to the touch from the sun, and that warms the bunk end area up.
PUGS almost totally eliminates that condition. I keep a cheap $16 box fan going all day as well just to keep the air moving around. While I like shady spots as much as the next guy, I no longer fear direct sunlight like I did with my old Class "A". That thing was an oven in direct sun.
FROG Member MO-0008-571 Since 2012
2016 Rockwood Signature Ultralite 8329ss (coming soon)
Nights camped 2016 -9
Nights Reserved 077121212125 ..........
My Project Blog: http://cowracer.blogspot.com/