Roger:
Good luck. I see why you have your pressures where they are. I think mine is too low at 6.5 on the low end.
I found a thread from Dec by a guy named Perry who is VERY knowledgable about the function of APAP's. IF you haven't read it , it goes into the mechanics of detection and interpretation by the software - very techy - good stuff.
As far a naping & feeling like crap - I just remembered I haven't taken a nap since getting on xPAP. I tried once but couldn't get to sleep.
Best Tom