If you use 3ft. rods with the long leg down you have to hold the rod in a different way which would stop it freely rotating. holding the short leg the weight is in the long rod so all you have to do is balance it so it revolves freely. Try it and you will answer your own question.
If vertical they're free to rotate 360 degrees.
If horizontal then the longer the horizontal the more prone to rotating at random when walking along or when prompted by an experienced operator.
Lozz.