Head it back across, and finish the knock-back. The back-post man nods the cross back into the six, and the second man times his run to finish first-time.
A cross to the back post is headed back across the face for a second attacker to finish. Emphasise the back-post man angling the header back into the danger, and the second man timing his run to attack the knock-back. Rotate the roles.
Fork it into your private drills, then change the animation, adjust positions, swap equipment, or drop it into a session block.