Your graph is interesting, but unfortunately its not based on actual data. You could put the blue line higher by reducing the size of the fin, to a maximum of 1.2 x Vs. Thus saving weight and fuel.
My graph is generic and schematic, to assist in understanding what I'm writing. Of course you may put the blue line anywhere you like, but you would create a very unusual airplane if you put it at 1.2 x Vs at maximum takeoff weight. Since V2 must be at least 1.1 x Vmca you would severely compromise takeoff field length requirements at all takeoff weights.