Because there are no fuselage fairings for linkage, the servo linkage needs to be all internal. The linkage is very simple.
Here the rudder post is cut away for clearance and guides are installed to receive the plywood servo tray.
Here I used two brass control horns epoxied into the rudder. The wire is held in place with small collets with allen screws.
The leading edge of the rudder is notched for full rudder throw each way.
As you can see the servo is captured buy the guides and the linkage arms. The rudder and servo are held in place with a typical piano wire hinge system.
The servo is a Hitec 615 MG metal gear for those occasional rough landings.