Tween is another one of those "in between" boats. it has a flat bottom for the most part like my Moby Dink, but that bottom twists into a V bottom entry like that of my WeeVee dink. The original Moby Dink, which can be built without thinking, is fairly stable and roomy for such a small boat. But in rough conditions she is easily stopped. The v bottomed WeeVee dink, on the other hand, hops over the chop like duck but would be too tippy for use as a tender where you need to step down into the thing from another boat. I'd expect Tween to be between them and be a good stable pram which can cut a bit of chop due to its twisted V entry.
Ed Heins of St Johnsbury, Vt., built the prototype to perfection. Ed reported the V entry cuts through the motor boat wakes common on his lake. (I should add that my own boat Twixt, very similar to Tween but 11 feet long, is also quite good that way. Pete James who built Petesboatwith the same hull shape but 24' long, said he felt the twisted bow was probably not worth the effort. I get the impression that the smaller the boat, the more effective the V entry bow.) This little boat has plenty of capacity for the 200+ pounds of Ed plus the weight of his son. Also you can see the lateen sail Ed and wife sewed up from the instructions given in the plans.
I drew a lateen rig for Tween, unlike the gaffer I put on the other dinks I mentioned. I think it will be easier to set up. (That's the only disadvantage I see with the gaffer.) For storage of the long lateen yard, I've shown an idea where the yard is folded switchblade like with the sail still tied to it. Ed says it all works great!
As for hull construction, two sheets of 1/4" or 5MM plywood will do it. Because of the twisted bottom panel, the chine angle rolls and this boat is best built as a taped seam job.