I've noticed a lot of people on this forum saying they have trouble breathing/can't breath at all when they press their tongue up against their soft palate.
Is this a 'must have' sign that you're mewing correctly, or does it depend on how recessed the face is?
I don't consider it a must-have, and I do think it depends on the recession...but not "how recessed".
I don't believe I've been a mouth breather, but I certainly didn't keep my tongue up. I never had the breathing issues a lot of people have had, and I think it's because I have a better air pathway compared to those who possibly mouth-breathed as well as had poor oral posture. But I'm not sure.
This is not to say I have better overall function than other people, because I don't. I just possibly have different dysfunction.
Yes usually people who have a very recessed face suffer from this. If you have a cephalometric x-ray and your SNA angle is say 78° it's very likely you will have this problem versus someone with a more forward 83° angle.
my story: http://www.aljabri.com/blog/my-story/