Having troubles interpreting Nick Schades book instructions wrt. paddle construction (A top notch book by the way). Any experiences out there, Nick perhaps?

My confusion comes at the stage when I am about to attach the blades to the shaft. The blade attaches longitudinally to the shaft, however, its orientation to the shaft is a mystery to me. The book includes a diagram illustrating the position of the blade tip and shoulder tip of the blade wrt. the leading and trailing surfaces of the shaft (My def'n of leading corresponds to the convex blade surface, the one furthest from the paddler). I have no problem with the blade tip position (blade tip flush with trailing surface of shaft), but the shoulder tip is also shown as being flush with the trailing surface of the shaft. Is this the intention ? This type of positioning of the shoulder would create no protruding rib on the trailing (concave) surface at the shoulder of the blade, a situation that seams to be shown otherwise in some of the photos.

In general, how large of a protruding rib is desired at the shoulder (on the leading surface, and on the trailing surface) of the paddle?

Thanks in advance...