8178,

I think we're talking about two different things....

I thought the question was about roll couple with rudder application. When upright, if right rudder produces right roll, then when inverted, right rudder will produce right roll. Sure, the model will yaw in the opposite direction, but the wings' dihedral causes the model to roll the way you want.

If the model has no roll couple with rudder application, then upright right rudder produces right yaw when seen from the ground. When inverted, right rudder will most certainly yaw the model to the left as seen from the ground.

As mck stated in the post just above, it turned out the wing wasn't straight. The first thing any airplane must be is absolutely straight. Insuring everything is absolutely aligned and straight is also one of the most challenging jobs when building a model. A lot easier to talk about than do. (ask me how I know!)