I know you are going to think I am a crazy old lady but eventually you could learn to close off the back door from your airway into your mouth and it won't matter if you yawn, or talk, or whatever....and no air will "whoosh" out your mouth.
I can do it (many others as well)....I can talk, open my mouth wide, even stick out my tongue and blow raspberries with mouth wide open...all with mask and machine on...without any air from the airway entering my mouth.
There's a reflex action that shuts the door in the back of the mouth. I can't describe how to do it on purpose though.
It's sort of similar to what happens when we blow up a balloon and no air comes out the nose....we don't know just how we do it but we do it.
I can't guarantee that you will learn or have your body learn to do this reflex action....but it is possible.
I think it took me about 6 months to realize that I could talk normally and not have air rush out.
And yes, sometimes the mouth drops open but that doesn't mean air will rush out or you are mouth breathing....it's just that little reflex action practicing on you.
In the meantime....if you need to yawn then yawn. Most yawns are in the head anyway....I know that when I type the word "yawn" it makes me have a really strong urge to yawn and I am not the least little bit sleepy.
Ever watch someone yawn and in just a short time you have to join in???
Unless the mouth opening leaks are big or waking you up a lot....don't worry about them for right now.
My mouth comes open occasionally but it's short lived. I probably do a little mouth breathing at times but I learned a long time ago that sometimes trying to fix little problems ends up creating bigger problems.
Give yourself a bit of time before worrying about mouth openings unless you are having major problems sleeping with it.
I may have to RISE but I refuse to SHINE.
If you want to try the Eclipse mask and want a special promo code to get a little off the price...send me a private message.