A small 5.5 is for most shaping, the 11" is the most used sanding bar I own, and the 22" is only used for sanding ribs even and leading edges. I even have the contour sander, but rarely use it, unless the plane has that exact prfile on the leading edge. Start light and stop frequently, run your hand over the work piece with your eyes closed, you'll feel the imperfections before you see them. It's better to under sand the plane than over sand it, going thru cap strips and making sheeting too thin will cause problems with durability of the model.