I am curious: when hovering, the F35 has a large almost vertical panel projecting from the top of the aircraft. This is presumably open to uncover the vertical air intakes , and is closed in fast horizontal flight. In the above videos I note that it also remains open as the F35 takes off from the 'ski jump', as the aircraft has to use downward vectored thrust. However, the extended panel must also produce enormous drag at a time when rapid acceleration was most needed. At what speed is this retracted? The force of the air on the panel must also be considerable by this time.