The funny thing is, that he only time I'm sure for the kill and I know it's just a matter of time to prevail, is when they start to manoeuvre, because the rear gunner then, ceases fire. I follow them aiming, with deflection, at the center of their upper wing. Two or three bursts and it snaps off.
I stay away from them when in formation and only if I have speed, height advantage I BnZ taking repeated snapshots till they brake off the formation. (it works better when your wingmen are doing so keeping the gunners occupied.
I never try to attack from below, (blind spot), as the gunners fire at me from impossible to aim angles and I most often end up severely damaged or dead.
Well, of course if they're firing at us through their own fuselages or doing similar crazy things with their guns, it makes it kind of tough to apply rational tactics ourselves - hopefully this will get sorted soon.