I considered using a kreg jig and biscuit joints but I am planning on gluing the whole thing together then seal everything with epoxy resin and hitting all the corners with fiberglass cloth and a finish coat of resin. It will be water proof and very strong.I know i'll be in the same place as that ill fated sunday morning on the beach in my friend's mom's Hillman minx, but here goes . . . .
most of the construction is built depending on the shear of your fasteners ( https://en.wikipedia.org/wiki/Shear_force ). which in some instances look like finish nails from a pin nailer. if you could build under compression (sides rest on top of horizontal components) there will be more rigidity in the structure.