A leaping lead hook can catch people out cold,safe only if you time one off their movement exactly; but you would want to have palm in and little finger down if going for the chin or you'll break it with that weight moving forwards behind it over a distance.

In close depending on the target palm down but both can work to suit your own movements and the target once again. When moving out towards the side like slipping down under their arm and then going for their ribs, palm down flat punch seems to fit naturally and to double hook down then up I like the turn and force of changing them. But its distance and target.