Duals are nice and will work OK with the 8 row head but you must have a ladder extension and you will want the electric ladder lift as the ladder will be knocking down the next row of corn when the guess row gets a little narrow. As for the duals and the 20' flexhead. If you are generally cutting straight back and forth, then it will work. If you have curves and turns, the duals quickly start running over the uncut crop.