Pontoon Boat Hulls - Why Round?

The cat form is somewhat sensitive to weight shifts along the long axis, even though athwartships quite stiff. I think what is required here is a summary of the duty requirements, including the areas of use, certainly if there is a call to traverse long distances, at speed, across choppy water, the difficulties multiply, and the possible solutions narrow somewhat, and the costs go up substantially.

 

It sounds to me like what you really want is a Deck Boat. A deck boat is cross between a pontoon boat and a catamaran power boat. They are faster than a pontoon boat but at the same time don't carry quite as many people as a pontoon boat, but far more than a monohull of the same length. This is just one example: http://www.nordicboatsusa.com/?page_id=62 Not all deck boats are twin hulls but some are and offer the kind of stability you are looking for while still able to get up on a plane.

Also to answer your question: round pontoons also minimize the number of welds needed, at the same time maximizing the volume, thus load carrying ability.

 

If he wants speed and 15 people on board, the cost is going to be high.