Flex settings ...

I currently am using a Respironics APAP (set 8.5-12) with pretty good results except that I occasionally mouth breathe - which tends to wake me intermittently or early. Switching it to CPAP doesn't help, nor does using a FF mask (I've tried 2 now and it just introduces other problems). Tape would freak me out. I tend to mouth breathe more as the pressure gets higher - but it is not a direct relationship. The APAP seems to help in that I clearly need different pressures on different days - especially with all the allergies here.

Has anyone ever set the flex setting (in my case, A-flex) to a number greater than 2? If so, did you find any improvement with mouth breathing?

And what is the difference if I use C-Flex vs. A-flex?