This piece is one of the few that is not done by The Book. The Book calls for a hidden piano hinge inside the trailing edge. I had significant difficulty getting this to align and work properly. I eventually discarded this and just went with the natural rigidity of the fiberglass and the excellent form-fit it has relative to the front strut. There are two screws that hold it in place and I believe that this is more than adequate retention.
Alas, I got a bit too confident with the process of drilling and tapping the holes for said screws and discovered that it indeed possible to break off a tap. I used a dremel grinding drum to dress off the broken fragments sticking out, drove to the local hardware store for a replacement and was more careful putting in another tapped hole 1 cm away. The two screws aren’t exactly aligned, and that bothers my eye, but it serves as a good reminder of how to be a careful builder.