Chas, Twevle foot long lumber is plenty. I use eight to twelve foot long white cedar for most of my boats and they turned out really nice. what I do is cut the boards into three inch wide lumber. This I will plane to 3/4 inch thick and set aside until all the lumber is cut. I use three inch wide boards for a few reasons. They are easy to handle for cutting into strips. The thickness planer does not have to work as hard. My ten inch Craftsman Table saw can cut 3 1/4 inches when I have 5/4 lumber. And when using a thin kerf blade I get eight strips of wood just a 32nd over 1/4 wide that will be planed to 1/4.
After you cut the small boards, take the eight pieces and tie them together with elastic band. This will keep all the wood from the same board together. This allows you to but the edges together for a near perfect joint. Just flip the one strip over and the joint will match. Keeping the bundles separated will allow you to colour match both sides of the hull and you can put two strips on either side of the boat that are almost the same. Hope this is of some help. Rgards Erich.