A daredevil executes a high dive from a platform 30 meters above the water's surface. An inflatable cushion is positioned in the water to ensure a secure landing. The cushion undergoes a 3-meter expansion before gradually halting the daredevil's descent. Determine:
(i) The mean deceleration encountered by the daredevil as they were brought to a halt by the inflatable cushion.
(ii) If the objective is to enhance safety during the dive by reducing the deceleration, should the inflatable cushion's stiffness be increased or decreased?