This design is straightly inspired by George Greenough Spoon which is inspired by classic boat's hull. There is no tail rocker, all the tail rocker is dead flat, and come to a knuckle which start the nose rocker. The fact to have no tail rocker is a tricks for get speed, the wave will be looking at pushing the board forward, and generate high speed, but without tail rocker the bottom turn is really hard, or almost impossible, so the answer of it, is the flex tail! Once the board will be down the line, just after take off, the flex tail will react and flex, and take the same form as the wave. It's a very precise rocker adapted to each wave. Then after bottom turn, once the board will be stuck in the wave, the flex tail will come back to flat and keep generating speed.