Pairs of mahogony frames were constructed for the three hatches.
The upper frame of the pair is attached to the fiberglass headliner using clear silicone caulk. The lower frame of the pair has plastic screen stretched across it, held in place by a layer of silicone spread through the screen to the frame.
The secret of how the frames attach is seen here. The upper frame has a thin, but strong disk magnet embedded in each of the four sides (secured with two-part epoxy); the lower frame has a galvanized sheetrock screw, cut short and screwed flush into a countersunk hole. The magnets are available from sign shops (type used for name badges, etc.)