1. Open the Aircraft Editor
2. Expand the "Software Radio" Tree
3. Right-click "Output Channel 2" and select "Add Complex Input Feed"
4. Change "Input Channel" to Input Channel 4
5. Click on <<Graph Points>> then click the '...' button that appears on the right.
6. If you want the elevator to go up with rudder input, drag the graph point on the right downwards to match the graph point on the left, if you want the elevator to go down with rudder input, do the opposite.
7. Click Ok
8. Click "File->Exit" choose Yes to save, and enter a new name for your aircraft.