Rudder Trim
Most of my RV experiance is in a -3 with a header tank. So I'm not sure I'm totally qualified to answer this. But Van's said keep it simple and keep it lite. I like that idea. Once you've done your test flights and trimmed it true, there's no nead for a rudder trim. I flew feet flat on the floor x-country in the -3. Aileron trim is more common to augment fuel ballances. I added aileron trim to the -3, it was very nice.
-Bruce