Finally! Someone who gets what I'm talking about!
When you wear the XS properly, its sound is AMAZING. Wear it wrong, and it sounds like an open-back headphone.
So the way it should fit is like a circle. It's perfectly round. Now. Imagine a circle all the way around your head. It's round.
The XS' fit on your head should look as if they were a small semicircle, the whole circle going round your head. Almost hugging it, which is the whole MIND THE GAP campaign, hugging your head comfortably, but reducing the gap, making it look more natural.
With the drivers not too angled, not too flat. This will help you get a good seal, but just try all the clicks and see if that helps.
This sounds like gibberish but it actually works.