: In airplane design biplanes had an inherent problem-partially
: solved by shifting forward one wing, usually the top shifted
: forward, but twin tails less so. In water maybe there's no
: problem.

The inherent problem with biplanes was a lift issue where the airflow around one wing interfered with the airflow around the other thereby reducing lift. Offsetting the wings reduced the interference. Twin tails are a different issue entirely. They are typically installed on multi-engine aircraft to put the control surfaces in the engine wash to increase control at low speeds (control surfaces need airflow over them to work and engine wash provided an artificial increase in airflow for the actual airspeed). This is the same reason that rudders are put in following the screws on large ships, it allows for a smaller control surface because the water is artificially faster than the ship.

Build something you can apply to the exterior of the boat to test it BEFORE you start cutting on your boat. Experiment with it and figure out what works THEN cut up your perfectly good boat.

Brian