need help trying to locate structural roof frame

[jbourne84]

This is a 1991 western wilderness Alpine truck bed camper

***Link Removed***

I have removed the bezel to the roof vent and the air conditioner in an attempt to see what the ceiling/roof construction is made of. I was hoping to locate some sort of ceiling "stud" pattern. The vent and the AC are both framed with 1" square aluminum tubes. I'm hoping those 1" tubes run across the entire top in some pattern that I can screw into from above.

I cannot really tell if those aluminum tubes (at the vent) extend beyond in any direction.

I tried using my crappy stud finder to pickup what's what but also no clear results.

The total ceiling/roof construction is about 2-1/2" thick and from this little cross section it's not possible to tell which layers surround only the vent frame and which represent the entire roof.

[BHale]

A Zircon MetalliScanner m40 metal detector will detect aluminum, it's what i used on my Host Yukon to mount solar panels. ~$42 on Amazon

[Oregun]

You could remove ceiling speaker(s) and try probing for the ceiling support ribs
through the speaker holes.

[Kayteg1]

If you have time and weather for it- on cold and moist morning you will notice condensation marks who will be different over the frame, than on insulation.
Works even on wood frame, so getting in right weather pattern is the only issue.