since your yakima tracks are either screwed or riveted to the roof frame, i assume you could also screw/rivet the roof to other roof framing. once the holes are drilled , figure some sealant into the hole, and then rivet it down ?? that appears to be how my tracks, and solar panel brackets are attached.
yes...look down into the Yakama tracks/rails and you will see the screws, with a little white sealant at each screw. My FWC mounted 160w Zamp solid panel panel does mount to these rails with sliders inside the rail; my added 170w Zamp solid panel is mounted just outside the rails on provided mounting towers [with a special adhesive] that matches the height of the FWC panel and I added an aluminum "L" bar between the rails at the front edge of my 170w panel for support to and augment the towers. Both panels are at the same height and slightly above the two vents but neither interferes with the vents.
Yes, one could screw the top sheet to the roof frame; but, in my case I would have to remove the panels to do that, find exactly where the roof support beams are, place screws with sealant and then, for me, worry about leaks. Where and how many screws to place would be a guessing game for me. Water tight integrity is a priority for me.