RE: Great Planes Big Stik 40 -dihedral?
Shoulder wing designs like Stiks have a certain amount dihedral effect from the wing placement alone. So as long as the aileron servo keeps working, you will find it flys very well with a flat wing. Even with a flat wing, right rudder will roll the airplane to the right, albeit rather slowly.
However, I often see people wanting to remove the dihedral from low wing designs. Not a good idea, since using the rudder will cause the model to roll the wrong direction. A rather famous design, the Contender, has this problem.
More advanced designs attempt to completely decouple rudder and aileron response. Often they still suffer some pitch coupling to rudder which is usually mixed out at the transmitter.