Your whole project looks pretty good. You might be overbuilding the boat somewhat, how much do you want it to weigh? How much cargo is it supposed to haul? How fast is it supposed to go?
The next thing I would do is see how the design works. Rig up something where you'd sit, put a motor on it and test it severely to see if it does what you wanted it to or to see what it actually does.
Then, if you want to change things on the hull, you can add them to the boat and test them. Once everything is worked out, finish the boat as the new plug.
What sort of chopper gun is that one that you use?