This design is an improved version of the Simple Single, intended to carry two adults. It is a fraction longer, a couple of inches wider at the waterline, has a vee-bottom instead of flat, and has a larger sail area. Compared with the smaller boat, it has a better carrying capacity, deeper draught, about the same freeboard, and should have about the same performance in spite of the extra all-up weight.
To make the basic hull half a sheet of plywood more than the smaller boat (2½ sheets), and the centreboard and rudder take the other half sheet or so.
The rig is a ketch, to keep the sail area low and spread out, with a basic light-wind area (jib, main and mizzen) of about 85 square feet. Just for fun, I have as well drawn an assymetric spinnaker of about 45 square feet, which might make life interesting for a couple of experienced sailors. Set in place of the jib, it gives a total downwind area of about 10 square metres.
With jib and mizzen removed, the main alone gives a well-balanced "working" sail area of 55 sq.ft, and with the mizzen stepped in place of the main, the craft ought to be able to work to windward in a strong wind under about 18 sq.ft.
The carrying capacity is about 400 lbs, which is two medium sized adults plus lightweight camping gear. The boat itself should weigh about 90 lbs including sailing gear.