Today I ordered all my materials. Just to give you an idea, I ordered 2 cases of 1/2" corecell with 24 4'x8' sheets per case. I am looking at close to 15K $ of materials for the hull, beams and floats.
After studying the plans for a few days, I think that the methods used for assembly make sense and I will follow them closely. I have a few ideas of my own (cant help it!) that I will try. One of them is to use pre-manufactured fiberglass angles about 1" x 1" instead of "duflex" strips. There is a large amount of 90 degree angle joints that will be easier to make like this. Another is to attach the beams to the floats before closing them off to enable the taping of the joints inside the floats, not just on the outside.
The boat will be very light and open on the inside (no full bulkheads) but I am a little worried about the headroom. However, I see this as a challenge. It reminds me of a very popular french boat, the Corsaire. It is 5.50 m long but people use them alot and they are full of clever ideas to make the best use of the small interior space.