On a small plank wing .049 ship I'd still be tempted to put in a few degrees of offset. It probably won't make a noticeable difference on a small trainer either way. Since a little 1/2A ship will be knocked around more in the wind it might help in keeping the plane tight on the lines. I think on a big stunt ship there is the concern of rudder offset possibly causing some unwanted yaw during manuevers. You won't be worried about that with a little trainer.