In fact in very small waves where the gyro is not overpowered, a vertical axis gyro could work without any control system whatsoever. A horizontal axis gyro would also work a little, but the very high resistance to precession of the slew ring bearings used on these systems would significantly limit the stabilizing torque generated. Stabilization torque is not caused by the precession axis braking torque, it is caused by the precession oscillation rate combining with the angular momentum of the flywheel to generate torque in the roll axis. The precession braking is only applied to manage the precession motion to within a nominated precession oscillation range and in most cases also to limit the rate of precession oscillation so that the gyro torque created is effectively capped allowing the supporting structure to be designed to withstand a defined maximum level of load.