Phil-
Sometimes it's possible to wedge (without gluing) a spreader stick into the hull; an attached string will make removal easy.

I've used 'teeth' - short wood strips glued vertically, separately, to the hull and deck. These will help to align the edges as you put the hull/deck together. If you are having alignment problems, you can space the 'teeth' closely. I glue them with epoxy and then split/grind them off after taping the inside seam.