Thanks for the info, and good to know a stud finder works well.
My next issue is going to be the wiring, but I may have a solution for that. Instead of trying to run the wiring from the roof down inside the RV, I think I will run it to a receptacle on the roof. I had already planned on putting a receptacle on the side of the RV, near the bottom, so I could use the panel as a portable unit. My thinking is, with that receptacle, and one on the roof, I could make a connecting cable, and plug them together once I have camp setup, and unplug it before I leave. If that makes sense.
This is the connector I planned on using. I will 3D print me a little box for the roof plug/wiring to fit in:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1