During this tour:
1 - Flying B17. Every time someone has attacked my B17, he has been shot down. I've only got killed by surprise attacks, else the attacker is dead, and sometimes me too.
2 - Flying 109G10 3x20 against B17. Every time I attacked a B17 (any angle) I've been killed. Sometimes the buff has been killed also.
Now lets talk a bit about play balance. A single buff can negate fighters at a single airfield bombing the hangars. Actually buffs have a laser precission against ground targets, so, a single buff can cause critical damage to any base. If we give them the hability to kill easily any single defender fighter, we have created a monster.
About the 50s of the buffs, try to hit a P51 from another P51 at d1.2 with all the six 50s concentrated at the same point... impossible, right? Now try the same firing the 50s from a buff against a P51 at d1.2... P51 dead if not evades violently.
IMO, the precission of human handled weapons mounted into a moving platform should be "poor" compared to 6x50 mounted into the wings of a P51. The recoil, vibrations, etc, etc will affect directly to human hands and arms. So, my conclusion: Buff's 50s are death rays with no doubt.