How to mount solar panels thin plywood bighorn roof

Assuming your roof framing is 16-24" OC, why not put a piece of aluminum 2"x?x1/8"+ or equivalent to span the framing members. Then fasten the solar panels to the aluminum strips. I would use pointed sheet metal screws for the aluminum strips. Self tapers in thin aluminum could strip out too easy.
I would also run the fasteners for the solar panels up from under the aluminum strips using counter sunk machine screws. That way you only have the bare minimum required screws into the roof.