It's not just the slide adjustment that needs to be considered. The length needed for each ear can be different.
There's also things like the type of ear pad, the head pad & where you position it on your crown and the clamping pressure of the headband. If you wear glasses then you must also consider the type of frame you have: Thin wire is better than thick plastic and makes the gel filled ear pads worth their weight in gold...
Only adjust one thing at a time, wear it for a long time & over a number of flights.
Take the time to try to identify what aspect of the headset is causing the discomfort & readjust for that thing.
Repeat ad-nauseum
Once you find a suitable setup, tighten everything up to prevent it getting moved.