I am quite suprised that this has not been brought up yet, but anyway, here we go:
The combat trim in the I-16 does not quite the job it is supposed to to. Instead of roughly keeping the plane in stable level flight, the I-16 banks constantly to the right. This is very annoying, since you either have to constantly retrim manually or constatly apply opposite aileron imput on the stick.
It looks like that combat trim does not center the ailerons properly. Did anyone else notice this too?