I chose the largest form for the Panache as a starting point for the shape of the cradle.  To account for the thickness of the padding, I traced the outline with a small offset from the form profile.  I tilted the form slightly from vertical so that the kayak would rest against the back of the cradle.

On the graph paper, I sketched in a flat base that I intended to make from a wedge-shaped solid piece of wood (to provide the horizontal surface to set on the Thule bar).  The wedge idea didn't work out well, but I still used the outline to create the shape of the laminated base.