My opinion is pretty much an echo, 6+2/2+6 or 4+4 (rare IMO but workable). 6+2 really works like how Nuke says it in a way, added kill power but without wasting too much of the craft's potential on that Circe or Lamprey gun.
The thing I don't like about three banks is that you're wasting valuable seconds changing the gun slot to fire. Granted FS could use a better gun linking system but the only solution I can think of would still make weapon changing slower than it already is.
Since time is one factor that counts in FS fights... heck, some community missions have already shown that every second counts... and even then it's still not enough...