Before you get to carried away with your design Nick very kindly helped me with mine (still on drawing board, money being the main reason). I also initially thought of a semi circular hull cross section but after Nick crunched the numbers there wouldn't have been enough buoyancy. Now there is a relatively flat section to the bottom of the hulls.
The semi circular design had approx 250mm (10") of draft with 180kgs on one hull or 100mm (4")of draft with 80kgs on one hull.
The non semi circular design had 200mm (8") of draft with 190kgs on one hull or 120mm (5") with 90kgs on one hull, with a slightly wider flatter section between the Center board and Main beam the depth of draft would be even better.
I found an interesting article not so long back (can't find the link now) but instead of using foam (core cell) strips along the length of the hull they decided to lay a lot wider 600mm (24")foam vertically they reckon the benefits were stronger, lighter and fairer. I guess you have to be pretty handy with the hot air gun whilst forming the required curves in the core cell.