Mask/mouth leak question

This is my first post but I've been lurking for several months. I was diagnosed last August and began CPAP around that time. I was sold an F&P Icon Premo and used a Airfit F10 full face mask for the first several months. Initially I had a lot of problems with leaks but after getting the pad a cheek mask liner and a better pillow I was able to get it under control. After a round of allergy shots and having less nasal congestion, I've been trying to switch to nasal pillows, Airfit P10, and with nasal pillows have problems with mouth leak even with a chin strap.
I'm not able to get any data from my machine other than what shows on the screen. (Another issue entirely.) With the nasal pillows it showed leakage in the 60's. Last night I went back to the FFM and leakage was 45. Should I try something other than the chin strap to stop the mouth leak or just go back to the FFM? I've seen mouth guards mentioned and also tape as methods of dealing with open mouths.
Thanks in advance for your help.

If you feel more comfortable with the pillows many people do tape their mouth. If you are not comfortable with that, its back to the FF mask.

What machine do you have?

The machine is an F&p icon Premo as I mentioned in my post

I have gone the same route that you are on.... I now use a Cervical neck collar to keep my jaw closed. you can also use tape with it if you need to

You can see from my picture why I need a to keep my mouth closed

Can you sleep on your side with the cervical collar?

Yes I sleep on my side all the time