Changing from full face to nasal mask

I have been doing generally well for the past year with an Airfit F 30 full face mask and settings of 16-20 cm H2O. The only problem is that by the time I awaken in the morning, the mask is uncomfortable because of the pressure around my mouth. Following some of the advice I've read in this forum, I've been trying to change to a nasal mask, namely the Airfit N 30 i. I have only tried it a few nights so far, but find at least for now, I need a chinstrap to prevent mouth leaking after I fall asleep. Exhaling through my nose against the pressure of 20 feels a little difficult, whereas I didn't even notice it wearing the full facemask. Would it be reasonable to try the EPR set at 3 to see if this makes a difference? There is not much of a range to work with - my minimum pressure is set at 16 because I had more apneic episodes at 15 or lower.

Thank you,
Richard

EPR is a great idea.
Some providers neglect to use this feature.