I think the chief rattle component comes from the contact of edge of the sliding window that is nearest the front of the coach ( the metal that holds the latch ) and the middle window brace while the window is in its closed position. The reason these surfaces are bumping against each other is that the window assembly isn't stiff enough for the forces it encounters. As it flexes, the middle parts move the most, and that's where the rattle presents.
I also get a lesser rattle from the screen slide there, but that could be fixed with a bit of Velcro to keep it from sliding during travel.
The net result is that you may see me driving down the road with my hand on the window to act as a stiffener so that I can carry on a conversation with my wife.