To extract more speed, and endow the boat with greater high-speed stability, in both pitch and yaw, "K7" was subtly modified in the second half of the 1950s to incorporate more effective streamlining with a blown Perspex cockpit canopy and fluting to the lower part of the main hull. In 1958, a small wedge shaped tail fin, housing an arrester parachute, modified sponson fairings, that gave a significant reduction in forward aerodynamic lift, and a fixed hydrodynamic stabilising fin, attached to the transom to aid directional stability, and exert a marginal down-force on the nose were incorporated into the design to increase the safe operating envelope of the hydroplane. Thus she reached in 1956, where an unprecedented peak speed of was achieved on one run, in 1957, in 1958 and in 1959.