Bill,
Just a suggestion: glue with epoxy (wear nitrile gloves) and seal the seams with vinyl caulking, paint with matte black on the inside or use polyester that black pigment can be added to (should be available from a boat/marine supplier). I have no experience building a pinhole camera having taking the lazy man's approach with an Ilford Titan.

http://www.jeffreyglasser.com/