supine, fetal, or sitting make more sense. Prone is for the rifleman. In typcical pistol scenarios, going prone doesn't make you a smaller target,cause the guy is 6 ft away or less. All that is achieved by going prone is putting your head where he can KICK it. Falling backwards at leaves achieves the goal of getting your head and neck out of his reach, and putting you where you can stomp at him with either foot. This is a VERY effective technique. I've yet to see even a TRAINED man who could get past that defense, when I put it on. Without real foot speed, and ability to BLOCK the kicks, kick accurately and VERY swiftly yourself, you WILL get your leg broken trying. So it's a VERY effective move to make against a knife man. Especially if the deck is slippery enough to make skip-kicking likely to result in a fall.