The other thing to realize is the convergence of the fighters coming in. I may be wrong, but most everyone I talked to has their convergence set at 400 or less, 300 being the average. That allows your bomber to have a little more reach on the fighters.
Not really.
The guns of a fighter are grouped much closer together than the 3 planes of a bomber formation are. For example, the P-51's gun batteries are about 20 feet from each other. If the pony pilot has convergence at D400, the spread will be 20ft at D800. Compare that to a B-24 wingspan if about 110 feet.
On the other hand, the distance between the three "hit areas" of a B-24 formation is about 70 feet each. Compare that to a P-51 wingspan of 37 feet.
The fighter can fly between those groups. The bomber can not.
I have all my convergence set to D350, but then I fly American fighters like the 47, F4U or Pony, I open fire at D1000, often having shred a bomber wing by reaching D800.