RE: Aileron Trim
If using the nextar's autopilot, and gain is too high, you can have a lot of trouble turning. (but that would be both directions...) However... with the extreme trim setting...that may be the amount of trim needed to overcome the autopilot when cross-correcting for a MINOR rudder trim problem.
Double-check that the rudder is straight in line with the vertical fin... Its one thing that you have not mentioned. (don't correct the nosewheel causing a turn on the ground with the rudder trim, make sure the rudder itself is aligned correctly for flying.... then adjust the nosewheel at the servo connection.)