I had the same type of squeaking that you're describing on our last coach (2013 Journey). It was difficult to determine the exact location because 1) it wasn't constant, only when induced by road conditions. 2) at times is sounded like the slide above me as you describe, and other times it sounded like at the window area.
In the end, I finally identified it as coming from the drivers side window blind. It was coming from where the blind fits into the steel mounting brackets. I was going to remove them and apply a lube of some type but before I got to it, we sold the coach
Anyway, just an example of my annoying squeak source
cheers,
Joopy