I always hang legs down, being taught by a butcher I assumed this was the proper way to do this task. To me is makes more sense to hang from the hock with grambel as I skin my animal asap to allow proper cooling of the entire carcass. Plus this way I can remove all the portions that are not processed for the freezer (hide, head, legs, etc) and just age the meat. If your doing a shoulder mount head down is the way to go for hanging.