If you really need to try EPR
11cm EPR1
Here's my interpretation, for what its worth....
If the flow narrowing is indication of airway narrowing, beyond all the possible reasons for this, it is the hope of pressure to splint the airway open.
The pressure range you are using is allowing the exhale pressure to drop to 8 or 9 depending on which scenario you have posted.
That is enough to allow the airway(s) to narrow over time, so.....
Adjust pressure so it stays at a point that will keep/splint airway open.
10cm may do that and reduce the OA events that are a result of too low a pressure as above.
The problem with the EPR, in my theory, is even when you get the exhale pressure to 10cm while using EPR, the EXCESS inhale pressure can/may actually contribute to CLOSING the airway !
I am not a scientist, sleep doctor, sleep clinician, I am simply reading the information that these people all provide.
There is easily enough evidence out there combined with practice, that would sanction these settings i suggest.
So,
I suggest 10cm as a constant pressure. No EPR
See how the flowrate chart responds.
See how the OA events respond, and it should give enough evidence to make small further changes.
But, most of all, See How You Feel !?