We started by making a template for the opening, locating where the hole will go from the inside, drilling a template center-hole through the roof, and using that to position the template on the outside. The Maxxair's frame corners have about a .5" radius, so I use a 1""punch.
Next step is taping the outline (inside and out) and punching out the corners.
Using a dull scalpel, I cut along the hole outline
Thus creating a place for rain to go if we ever want to turn the sleeping bed into a garden bed
After a bit of smoothing rough cutout edges, and ant-rust painting the raw edges, the frame fits
Cleanup and beer break
The frame is screwed through the roof into plywood strips. The strips are being held to the roof by VHB tape, so I gave the tape a good squeeze to make sure there is good roof contact. The screws are stainless, so there should be no electrolysis issues screwing through the roof. There are strips on the other 2 sides as well, but no pics of that.
The frame is screwed in over several layers of caulking strip, squashed out excess is trimmed off, and we cover the thing in vanilla icing (actually a copious amount of lap sealant). Don't hire me if you want a neat job squirting sealant (or cake icing).
Finally, mounted the fan in the frame
Closed the fan, and we're done.
Next steps will be insulating the floor and walls, installing the solar, insulating the roof.