Some lifters have trouble hitting their backs, even with back exercises. Often, the biceps take over. The unilateral lat pulldown allows you to really focus on the back one side at a time.
Do not fully extend the arm at the top of the movement.
The Shotgun Method allows you to train for both size and symmetry without having to skimp on either. It actually allows you to concentrate on the big lifts without neglecting isolation exercises that address lagging body parts.