Go large

I've just decided to make the boat slightly larger by adding a fourth rib set. (It's identical to the middle rib in the picture a the top, so there are two wide ribs in the middle and two narrow ribs in the bow and stern.)

This will increase the displacement from about 300 lbs to about 425 lbs. With the three-rib boat, I could go out with one boy or the other, but all three of us together would be dicey. This way there will be room for all of us.

I think this is a good call, and will not affect the fundamental difficulty of the project.