[Treatment] AHI skyrockets when going from double to single pillow?!

[Cpapaya]

   
       

I've recently been having some neck pain, that may or may not be related to a frequent feeling of faintness/dizziness. Originally I sought CPAP treatment for this same issue, which was only mildly relieved from treatment (1.5 yrs in).  I've been seeing a physiotherapist who recommended I switch from two pillows to one. I used one pillow a long time ago (pre apnea diagnosis), but switched to two with the idea of alleviating symptoms. I also use a snore guard.

Attached are two OSCAR readings - one with two pillows (AHI 2.8. the night prior), and one with a single pillow (AHI 8.79, last night). It occurs to me that at the testing centre, I also used two pillows.. so maybe my pressure (of 8) is too low to properly support a single pillow setup? I am a side sleeper, and the single pillow I use is definitely on the firmer side - I'm not sure about a perfectly straight neck while sleeping.

I'm also considering a cervical collar, but of course with these current neck issues, adding something to the mix might not be a great idea at the moment.

Is there anything standing out as obvious to our experienced readers here, that I ought to consider?

(Edit note: my profile states nasal F&P - I switched to the Resmed F30 on forum advice, which did seem to improve my overall score and outcomes).
(Edit: Based on what I'm seeing in other posts, I've added a close view of the OSCAR data worst spot).

[Phaleronic]

You're likely chin tucking, a camera to record what you're doing during your sleep positionally may be of the most help here. For now I would turn EPR off since you're at 8cm in cpap mode, this should clear up some of the CAs and help the OAs a bit, also try to sleep on your sides as much as possible, you can keep the slightly thicker pillow with these settings and trying to sleep on your side to see how it goes.