The vast majority of fighter planes in WW2 COULD NOT adjust all axis of trim in flight, like we can in AH. In the case of the P-40E, the aileron trim was adjusted on the ground.
The Bf-109, as another example, only had pilot-controlable elevator trim; neither the ailerons or rudder could be adjusted in flight.
Stuff like this is why I question even bothering to have trim at all in a computer game--it simply does not work like the real thing and has far too much of an effect.
J_A_B