This is the philosophy I'm looking to use because it plays the odds. Level II covers most carried handguns and I believe 00 buck. Though while I doubt I would ever likely need the extra IIA for 44 mag and 9mm submachine gun, the extra impact protection may be better considering I likely will not have backup for the recovery time to return fire. It's useless if they walk up and shoot you in the head while your eyes are rolled back because a cracked rib hurts sO much. Level III just seems to heavy not being in combat.A good general rule to start: have a vest that protects from the caliber that you carry at a minimum.
I don't like the extra weight of the chainmaile. Though most people don't seem to know that using a knife means the arteries are better targets than a stab.Also you may want to take a look at stab plates. That's a much bigger risk than being shot.