I wouldn't expect much change in 500 ft, otherwise we'd be running in-flight mixture control for anything above 1/2 box height.

The type of change I'm referring to is dropping 1500 ft, starting up in the morning cold and having your engine hesitating a bit on throttle up. Just enough to be noticeable and have you reaching for the screwdriver with one hand while crossing your fingers with the other, hoping that it might just go away when the engine warms up a bit more so you won't have to touch the regulator.

That being said, I haven't been able to get to a sea level field since I've sorted the engine, so the mixture may be more flexible than what it used to be.