Graviman is quite correct about dihedral. It is commonly thought that dihedral is needed because most of us start out with free flight balsa models that have lots of dihedral. But a piloted craft needs no dihedral. I finally understood that after flying an Extra 300 radio control model when it flew straight as a bullet. All aircraft have "roll damping" that slows the reaction and allows the pilot to maintain control. Dihedral is not needed.
slowrotor