For the past month or two ive really focused on the posterior third and even though its expanded to 41mm! im still having so much trouble breathing with good posture. I started to disregard the tip because i saw a few posts saying the back in the only important thing and that may be true but the front is important too. I read a comment on our reddit group talking about tongue ties and he brought up @test151515 "that to have sufficient air flow through the throat  is about having a tongue thats located enough forwards. this require a tongue that is strong and reaches far and a forward developed maxilla so the tongue can be placed forward sufficiently. Many people with underdeveloped maxilla and breathing issues have their tongue positioned too far down their throats reducing airflow" I belie this is exactly what was happening to me i completely  focused on the back and lost my posture in the front if your  having breathing problems this may help you out.