Thank you for the kind words.
Since pictures are better than words, here's an illustration on how fly rod bends in response to increasing loads. The increase in bend, brings the the rod tip closer to the rod hand; and the rod hand moves in a convex path to correct for the rod shortening so the rod tip can move in an SLP.
In the illustration below, Jason Borger in The Nature of Fly Casting
, illustrates the convex path using his finger as the rod.