I have narrowed rudder trim down to three options. 

1. Spring Bias mounted under the panel.
http://www.mlblueskunk.com/Rudder_Trim_System.php
http://www.aerosportproducts.com/ruddertrim.htm

Advantages – easy install, less points of failure (no electrical, switches, etc), also provides for light duty gust lock on the rudder as the springs will attenuate a little wind.
Disadvantages – not controlled by autopilot and if a yaw damper is used the servo may get more wear and tear, takes up space under panel in possibly congested area.

2. Vic Syracuse style rudder trim build with a hinge attached to rear of rudder.
http://www.myrv10.com/tips/mods/RudderTrim/index.html
Advantages – Can be wired “through” yaw damper servo and “run” by the autopilot to auto trim the airplane so when the AP is disengaged and the yaw servo turns off the plane will not “lurch” as it will already be trimmed. Nice panel mounted switch with feedback loop for position identification.
Disadvantages – More wire running to tail, another switch and indicator on the panel, potential re-balanceing of control surface, and breaks personal rule not to change aerodynamics of my build.

3. Nothing!