a.) I kind of imagine two over-sized quarter spheres attached to each other. I would say they each are 29% spheres, but look rather like right angled walls: the floor and the plane of attachment and then they both go upward a little into the air from the top of the meeting point.
thanks for your info. Did you get 29% from a calculation ? I have a video about but I can't up load it, maybe it's seeable at : https://docs.google.com/leaf?id=0B9pGxyM9yy2fNDMxMjgyYWQtNjQ0Ny00NGYzLTllOTUtMzFkNmIwNGY1MTky&hl=en