Make a plywood piece about 3" smaller in width than you need and prop it in place. Then using compass set on 4 or 5 inches, scribe the shape of the hull on the piece. Then take it out and back to the bench where you repeat process in reverse leaving an extra 1/4" or so and begin fitting it.. Or do this with a piece of heavy paper or 1/8" ply then make your piece after you are happy with the fit.
I am no boat builder but have fitted plenty of counters, stone pieces, floor boards, curved stairs etc. in houses and used same method every time. I use tar paper and a scrap of wood on horizontal surfaces.
On the other hand, shouldnt glassed in bulkheads have alittle space to the hull for flexibility?
You dont need to make a template that fits tightly is what I am saying, just a way to bring that shape to your piece.
Also, if the top of your bunks are above your water line, a hole in the bow would fill the space below them but if they were glassed to the hull/floor they would hold water no? Thought about glassing the rear panels of my bunks to the floor when installing my thruster for just this reason.