Our team used a heavily modified version of Kevin's PID code,
basically all you have to do is add another motor to the motor_info data struct, and change the get_encoder_value function so that it returns PAN_SERVO when the argument is 2
now simply call set_pos(2,127)
and set your left and right drive motors to =motor_info[2].pwm+127; and 127-motor_info[3].pwm; (this may need to be change depending on your wiring and robot setup)
you may have to tweak the P, I, D constants
We had it working beautifully until we did some other stuff and screwed it up...
(we used our own custom PID software... but i think i'm gonna switch back to kevins because i can't figure out whats wrong with ours... and I didn't write it so I don't understand it 100%)