Well, here is another modification to prevent the Headrest nose cushions coming lose and the back strap from sliding up. And this one is of the non-hacksaw flavor. In fact, I had tried this on my trial version from the DME, and returned it in its original condition when I got another one.
Summary: Two elastic bands are added starting from the top of the head near the existing straps, crossing behind the head, going under the ears and closing as chin straps with Velcro pads.
Details. In the pictures below, the head model balloon is smaller than the head for which it is fitted, so some of the strap lengths and postions are a bit off. I use, during the experimentation stage as in the photos here, regular paper staples to hold/attach the elastic straps, the staple open ends facing away from the head surface.
The elastic is about 1 inch wide readily available in fabric stores.
Top View looking from front. Each strap starts at the top normal adjustable straps, close to the plastic housing. The elastic loops around the top of the folded over original Velcro (rather than the bottom of it); this will prevent unraveling the Velcro. These are kept in place with 3 staples each.
Back View. The straps cross over each other, at a point under the original horizontal adjusting Velcro straps and continue downwards below the ears, to the opposite sides. I have used two different color elastics, the white is a continuation of the black (I ended up this way when I was experimenting). You can use the same elastic strip; it is easier.
The elastics are attached to each other and to the bottom portion of the headrest strap with more staples. You have to experiment so that when the final headrest is worn, there would be a gentle stretch on the portion of the elastic between the top plastic (starting point) and the horizontal starp behind the head. It is easier to adjust this later at the beginning of the elastic at each side.
Back view, a bit lower. The elastics continue behind the ears, around the neck to the front.
Front face view. The straps are attached to Velcro fasteners, with a brown fleece like pad under the strap where it will go over the chin, just below your mouth. [You can adjust the position of this to close the mouth a bit too, if you are so inclined. This may reduce mouth breathing a bit, but by itself it is not all that effective for that.]
Velcro closed view.
Optionally, you can add fleece sheaths to the straps which go around the cheeks to protect your beautiful skin from having any marks. Even without the fleece, the elastic is stretched only gently so that you may not see any marks.
Here is the resulting graph of leaks from one night, with my normal pressure at 5.5. I did not have any mouth taping this night. Yes, it is an unusually leak free night, I have little squiggles + or - 7 lpm other nights.