I find he can't hit at all if you treat him like auto ack and are constantly changing your direction. As soon as you stop alternating your path you are insta killed, definitely need cannon birds to do damage while moving.
The only problem with your method for me is I can't hit a thing with cannon. I can saw him apart with .50s from extreme range.
With the 190 I get too close before doing damage. With the 51 I can kill him from a lot greater distance. When you blow up one buff per pass you can survive the engagement even if you take damage. If you have to take a second run with three bombers flying he lands more rounds.
I don't maneuver as much as slice across--which must have a similar effect to what you are saying.
