The white line from the karabiner to the helmet is not part of the harness. It is elastic bungee attached to a pulley fixed to a chord around the back of the helmet. This arrangement takes some of the weight of the pilot's head and helmet. It relieves much strain on the shoulders, arms, neck, and back. (The pulley enables your head to turn normally.)

The author tried it once and determined never again to fly without one. I have flown with it ever since, even though it necessitated an additional chord to the back of the harness (not shown here) to prevent a tendency for the harness -- now partly unloaded at the front -- to rock head-up.