It does work well to calm things down. Used it a few years ago in Pulpit Harbor when a front came through to keep our distance from the other anchored boats.
Ours is a Hood sail, given to us by a friend, which hanks onto the backstay. It can be tacked to the boom, but is more stable if the lines are run to the toerail. Then of course it is an impediment going forward to check on things.