I don't have the impression that the 109 is weaker gunned. Actually when I score on Spits I usually have quick kills while I have to pump lead into the 109 when I fly a Spit.

I just killed 3 Spits with very little. After having killed the 2nd Spit I still had 11 rounds of my cannon guns.

It seems quite spot on.

I have full realism except for antropomorphic limitations.