if you are getting drift on an axis its a sign you need to recalibrate, then dial it out with deadband - regardless of what you're using it for.
seeing the gun drifting in GV mode means that you will get pitch or roll axis drift in an aircraft too (which will turn off autopilot if its bad enough.) likewise unwanted rudder inputs while driving will also manifest while flying, you dont want that either.
This is not a calibration issue. There will be some drift even if you are perfectly calibrated, due to hardware tolerances. That's why the deadband adjustment is there in the first place.
On the joystick horizontal and vertical axes, I use zero deadband for planes, because I am constantly making minor stick adjustments in flight, and the extra slop associated with deadband is undesired. In contrast, with GVs, I don't always have my hand on the stick (when lying in wait for example), so I put in a small amount of deadband to avoid this drift. The small sacrifice in controllability is acceptable.
On the rudder Z axis, I use zero deadband for planes for the same reason as above. In contrast, with GVs, I use a very large deadband setting. This is because I steer with rudder pedals; they have a lot of mechanical slop, and if you have any residual “turning” input from them, most vehicles won’t shift up. This is a consequence of HTC removing the manual gearshift feature from GVs.
I hope you aren’t one of those “my way is the only way” guys.
MH