When the H16 was new many cat sailors were still sailing straight downwind. Even after gybing downwind was accepted by the H16 racers many would still go straight down wind in light air. That is the reason for the boom vang eye.

Most of us have never raced straight downwind on a cat. So, we don't realize the importance of a vang.

There are some cats that go straight downwind (Wave, Laser Vortex, etc) The ones without a vang are just eaten alive downwind. In light a laser will horizon a Wave downwind. Even Lido's creep up on you.

If you want to try a vang some light air day. Attach a heavy bungee between the tramp lacing at the base of the mast and the eye. The bungee should just barely hook. A line tied tight will work too.

This is a useful trick if for example, the wind has died and the beach is dead downwind. You can vang it and go wing on wing.