Is it possible stretch headgear in a short time?

I replaced my ResMed Quattro FX mask and headgear in a single pack. I ordered the medium mask so I assumed I'd get a medium headgear. Previous purchases have been medium headgear which fits fine. This time it came with Standard size headgear.

So, my problem is that the loop that fits over my skull is way too tight, I feel like my head wants to burst through it and prolonged wear gives me a headache. I emailed ResMed and they said Standard is exactly the same size as medium. So I guess my only solution is to try and stretch it - any ideas please?

Chris

I guess it's possible, but, I have used the Quattro for over 5 years and the masks last me well over a year before I change them. I have never changed the headgear.