I recommend getting some Devcon Plastic Welder, which is a modified acrylic adhesive. This stuff will stick everything you use in a model sub, trust me. It's stronger than epoxy and totally waterproof. Once you bond something together with this stuff, the material will break before the bond.
Over on our Dive-in Facebook page, one of the members there is building a Dumas Akula, and has fitted a cylinder in it, not quite finished yet, but he's very close.
Not sure if you're on the big 'F', but if you are you're welcome to drop in and have a peek.https://www.facebook.com/#!/groups/133360626703083/