Maybe it's different in TTs and 5vers... I never really got into the walls of our TT's when we had them. I know some of the interior walls were hollow, but no idea whether it was to this extent.
No different in mine. The interior walls are worthless for attaching anything heavy. I spent considerable time reinforcing the platform my components sit on.
Below is an interior wall between a closet and the refrigerator. The 1"x2" was there from the factory. I added the two pieces of scrap plywood to improve the strength. A hanger rod with a shelf attaches to the 1"x2". It screamed out at me for some additional support. The pair of black/red wires on the left are coming down from the PV on the roof.
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