Jack, I was just in there doing some wiring today. I know what I see. It is single layer at the top. Take a look at the higly proffesional drawing of the roof vent installation again. You see the inner shel slope up and "Meet" with the outer shell. The carpet install drawing sort of gives a side view of this too.
Clicky here for Burros cutaway view of it.
The roof vent is not centered on a Burro
, it is off center toward the street side. the side of the vent farthest over towards the street DOES lay right on the edge of the double shell, but it is maybe an inch back. If you used long screws, it would puncture the hull there.
Every where else (On the 3 remaining sides) you can clearly see the screw tips.. and in my case, quite rusted ones.
The pictures you see on Burros website are of the Escondido wide bodies. They may very well be different, and most likely are. Different molds. (I have personally never seen one) I know what my Sac City 80 is like tho.