I fly the Polikarpovs a lot too, and I always avoid going head-to-head with 109s. That big radial is a hell of a target for a fighter with centrally-mounted guns to miss. While I might not get p/ked because the engine is good to hide behind for the aforementioned reason, it's the same end result if my engine loses power: the 109 pilot will take me out on his next pass while I wallow along like a duck.
The exception would be when the two planes turn in towards each other and I can see that the 109 pilot isn't going to be able to get his nose on me before we reach firing range. Then I'll give him a burst as close to his canopy as I can before I roll and break away. Sometimes that does the trick, especially in the type 24.
Bombers though, well that's the only way to attack the 111 or the 88. Straight on, throttling back so that the burst lasts as long as possible, and then inverting before diving away. They very rarely live through that kind of treatment.
B