The more of the pulley the line touches the better grip it will have - allowing you to set the tension lightly as recommended - while getting the maximum grip on the line to move the flag.
THE CONFIGURATION BELOW IS USED BY THE PROFESSIONALS BECAUSE IT ALLOWS FOR THE MOST LINE CONTACT WITH THE DRIVE PULLEY AND OFFERS GREATEST CONTROL WITH THE LIGHTEST TENSION - WHICH IS IDEAL FOR OPTIMUM RUNNING. Note: The number of additional field pulleys may vary - the main point being that there are two field pulleys closest to the main drive unit to keep as much line touching the drive pulley as possible.
You may also opt to place the main drive behind a fence and run the lines under so that it is not accessible to the running pups.