Hmm, imo hit the gap isn't worth taking, you would get a greater advantage from a lifegiver, a man of steel or an even tougher. Your build hasn't bonehead so MOS seems the best choice.
About shooting legs, well, legs almost don't have any rolls, if you crit the guy will fall, unless he is a stonewall. The only target you want to shoot in the legs are MOS tanks (265 hp + RL/gatling most of the time). Since the knockdown chance on a shot (taking into account the crit chance and the roll pass chance) is pretty much the same if you shoot groin or legs, you better shoot groin on other targets. Thus you will deal more damage, more knockouts and more bypasses. You can knock someone out with a leg shot but it's pretty rare. Leg shots should only be used on fleeing targets, at that time the fight is won, but you don't want your loot to run away do you?