I added a cockpit adjustable rudder trim on my Series 5 several years ago and at least on my airplane have found it a welcome necessity especially on cross country flights. I found my original ground adjustable tab to be insufficient , as the dynamics of how much rudder trim was needed seemed to change on every flight and I could not get the ground adjustable tab set for a centered ball to my satisfaction. The cockpit adjustable version cures this problem. Hobby shop supplied the high torque servo (mounted in the rudder like Gizmo did). Cost was about 150 bucks for the whole setup as I recall.Pictures of my setup are in the archives on this site. Bruce Lina N199CL