I made a short video of my rover driving a mission with active tailwheel control. Without the servo controlled tailwheel/castor, I never got the rover to drive straight, because every gradient would cause the rear to roll down that gradient and the stabilisation was not strong enough to counter it. Or if I set the PIDs high enough to drive straight, the rover would totally freak out when stopping. The tailwheel control works by feeding the throttle values for the left and right motor into an arduino, which then calculates the tailwheel angles with a little trigonometry and sends out the PWM value to the tailwheel servo. It also tried to use throttle and groundsteering values, because this would make the calculation easier, but each time I setup throttle and steering on output 2 and 4 (1 and 3 are going to the ESCs), I got different results. Sometimes the throttle would only go to +/-50 from neutral, or the steering value would jump around randomly. Yes, I know skid steer and conventional steering output at the same time is not supported and tested.