The president of my club had a similar experience when taking up a student's Nexstar for the first time. Pulled to the right real bad and just missed the cars in the parking lot! I am not sure what he had to do to correct it though. It sounds like the ailerons are trimmed for a right turn and the rudder is correcting for that once the plane is up to speed.

I think I would try trimming in some left aileron. Just a little at a time and see if that tames that right twist. Then you might need to trim a little right rudder to compensate for the ailerons.

Actually, it could also be the other way; in that the rudder is set a little right and the ailerons are compensating when it gets up to speed. This might make more sense since the rudder is more effective at lower speeds (ie. landings and take-offs) than the ailerons.

How about this: try setting your rudder for a little bit more left, but adjust your nosewheel so that it is still rolling straight.

Boy, I'm just full of ideas, aint I? You can tell I'm no engineer! But, I have been flying RC for about 15 years. And I did stay at a Holiday Inn last night!

Perhaps one of the more aeronautically educated types can chime in here!