Small ground robots remain limited in their locomotion capabilities, often prevented from accessing areas restricted by tall obstacles or rough terrain. This paper presents the improved design of a hybrid-locomotion robot made to address this issue. It uses wheels for ground travel and rotary-wing flight for scaling obstacles and flying over rough terrain. The robot's initial design suffered from a number of issues that prevented it from functioning fully, such as overheating motors, inadequate control electronics, and insufficient landing gear. Several improvements have been made to the robot's design to correct these problems. These obstacles, and the solutions implemented in the improved design, have enabled several design principles to be formulated for miniature hybrid-locomotion robots. It is found that hybrid-locomotion vehicles utilizing rotary-wing flight are most useful when the design is optimized for ground mode performance. Collapsibility is necessary in such vehicles to reduce the impact of the helicopter rotor on the size of the ground mode. Finally, since a large number of actions are necessary to propel and transform the robot, integrating multiple functions into each mechanism can reduce the mass of the robot.