waterskis do have some curvature to the tail rocker which is where the ski contacts the water whilst planning.
the fastest speed boards are flat in the tail, but wave boards have curved tailrocker.
also Bethwaite's book is incorrect on the statement that he makes about windsurfboards. he sure didn't see them as being possible holders of the speed record. the book is otherwise quite informative.
topspeed 40knots is an attention getter so the statement does work from that angle. something a little more creative would have been nice IMHO. they are preaching to the choir in our case anyway. obviously we all want to take one of those bad boys out for a ride.