Following are pictures of the aft bouyancy tanks coming together.
A blind fillet is made while you have access to the inside area of the tank. 
Glue on the tank sides: 
Glue applied on the blind fillet and glue cleats: 
Glue on the lid, held in place with tape and sticks; 
More finished photos will follow in another post. Had a meeting this weekend discussing the sail design with designer Sandy Goodall. Things are moving forward. Cheers...