Ok, stick with me now.
Short , manuverable boat transforms into a long and lean cruising machine. Nesting and 2-4 piece boats are nothing new. My take is a little different. Picture a two piece pirogue type boat about 16-17ft long with, say, a 24-26" bottom. Now the rear piece is not located around midships like in most 2 peice boats. It is located at about the 13ft mark. You're left with a front section that is basically a skiff with a somewhat smaller transom. Really handy for fishing ponds and short river and creek trips. When you want to cover some serious ground, attach the rear section and you have an all day cruiser. The rear section would nest easily in the front section for ease of carrying. The draft really wouldn't change much in losing just that few feet in the skiff mode. It's mostly skinny and wouldn't add much to the bouyancy anyway. Whatcha think?