I really enjoy looking at your builds, quit jealous of your pace (I think balsa shortage as a result of building windmills is a hoax, it's you building gliders 24/7 not!?)
The crescent shaped ply part on the rear cockpit bulkhead performs the twin duties of tying the two former halves together, and providing an edge to which the canopy can be glued.
The canopy frame is built up in place, with the starboard rail first being hinged up with brass doll's house hinges
When adding the ply sheeting, I always find it easy to apply it in two halves, with the join in the middle, over the short longeron...
Where possible, the joints are reinforced with short lengths of fine piano wire, inserted via the drill...