Hi Neil, as the onwards and upwards didn't help you let's try something else instead. Ten dollar question what are you building? Is this a kit, scratch-built, or whatever, what is the hull made from, plastic, fiberglass, or timber? Is the hull complete with fittings, as in wash-ports, hawser holes, prop-shaft, rudder, etc? I think a few photos would definitely help to clarify your present predicament and be very helpful for us outsiders offering advice. What will be your power source, (I would love you to say STEAM,) but that is probably unlikely as I do appreciate it is a little expensive. So basically the situation is a little more information please, and I shall consult the oracle on your behalf. Regards Gary.