Unusual way to cure air leaks - nasal pillows
Someone suggested and I tried it. I was having air leaks from my mouth, even with the chinstrap. Once I used an adult sized pacifier (found on the Net and looks like a significantly larger child pacifier) it totally solved the problem, usually resulting in an almost zero air leak issue.
One caveat, I was told that doing this may affect one's occlusion, so I asked my dentist to measure my overjet prior to doing this. After using this for almost 6 months he noted that my overjet increased by 1.8 mm which, for me, was an actual improvement (it was 1mm on day one) since my bottom teeth would often rub and/or bang against my uppers which no longer happens.
My sleep apnea was so bad that I'm willing to live with any further changes but you may not be willing to. I'm not saying this is certain to happen to everyone; it may not as one data point doesn't impart any trend, but I thought it worth mentioning.