[villagetinker]

I would go with a high quality clear epoxy glue. this type of glue is rigid, so I would then apply a flexible cover of GOOP marine grade glue. This product goes on easily and has a good life. I am assuming that you cannot easily get to the back or underside of the enclosure, or I would apply Fiberglas and the appropriate glue. If the crack is truly hairline, then the Gorilla Glue 'super glue' should be able to actually soak into the crack and completely fill it, but I would still have the Goop overcoat, as it is flexible.