The boxes will never be located on a ridge. They will be in a low spot, because you don't screw the panel to the stud on the high ridge. The boxes are always screwed to a stud.
Agreed. I’m also mounting some external lights on the walls, and that rings true for them.
But on the interior of the building there are some existing light fixture boxes located at the junction of the trusses and the purlins (I think that’s the proper term, not sure what else to call them) that I was hoping to use, and base the layout for my additional j-boxes on…..