I am just making the servo balance panels on an 1/8th scale 16.25ft span Handley Page HP42. They are separate surfaces altogether. These are hinged at the rear edge, so the airflow tries to push them further over when operated, helping to equalise the 'self centering' of the rudders themselves. Heres a pic of the full size. The whole lot works on a single closed loop system to the centre rudder.

Ian.