Lowering the crossover point.

[VolvoHeretic]

Um, that would be me. I would build a couple of wood rings and epoxy them to the inside of the cut end of the barrel halves so that they don't fall apart when you start shaking them. I'ts going to take a lot of glue to hold them together, although, if they work out nicely, I would fiberglass up the insides into one strong solid mass.

Edit: I mean a hollow ring at the open end and a solid one at the closed end where you are going to cut in the speaker to hold the multi-piece lid together (I think that it is multi piece) and then cut out the speaker hole out through both the lid and the reinforcing ring. Kind of hard to describe without pictures.