The reviews of the F20 have been very good, so I went to my "friendly" DME to give one a try. They don't like to take a lot of time with fitting but I did get them to let me it with my max pressure of 14. It took a little fiddling but I got it adjusted so it didn't leak. But I didn't test it to the extent I should have.
Now I'm home and have tried it again without any adjustments. Air blew out the sides between the bridge of my nose and my cheeks and the seal made an interesting sound. I pushed the mask against my face and the leaking stopped and did not resume when I released the hand pressure, until I moved my head. So I tightened the straps until the leaking stopped and did not start again. Seemed great, although felt a little tight. Took it off and put it on again without any adjustments; you probably guessed it, noisy leaking again along the sides. Leaking stopped with application of pressure and wiggling the mask slightly; until I swallowed! So it seems I can adjust this mask so it won't leak but I'm not confident that it will stay leak free through a change in position or a swallow or two.
I would appreciate advice from other users. I read somewhere that this mask may need a little time to conform to my face. Has anyone found that to be the case?
I wish I could use nasal pillows but I discovered years ago using a nasal mask that even with a chin strap I blow air out through teeth and lips.