Attack it anyway; aggressive action is your best hope
From Create Your Own Story
Before the gunner in the rear turret can draw a bead on you, you break hard right. You see tracers pass by, where you were. You are still behind this thing, which looks to be coming around again for another go at you.
You're pretty sure you can't outrun this thing. Fighting it may get you killed, but is also your best chance. You pull the nose of your P-51 back towards the thing. Giving it as much rudder as you can, and opening the throttle, you pull around toward the German plane, trying to cut it off in its turn. You hope your faithful P-51 can stand the abuse you are being forced to give it; you don't like the way it's rattling and shuddering, and you know it's only a matter of time until the engine tears the airframe to pieces.
This thing is fast and maneuverable, but it has to obey the same laws of flight as you do. With your engine screaming and shaking, black exhaust streaming from your much-abused Packard Merlin, you gradually pull into a position from where you can fire. You are behind it and a little below. You only hope the rear gunner can't get a very good bead on you from this position.
You offer up a quick prayer and squeeze the gun button.
What happens?
