My first one was the ResMed Chin Restraint. Totally useless. Kept sliding foreword on my head, even with one of my girlfriend's berets trying to clip it in place.
Next was the Ruby, size Large. Worked great for many months and I swore by it and bragged about it. Then it stopped working - mouth breathing, leaks galore, dry mouth. I thought it stretched out, so I bought a brand new one, same size Large. Didn't work from Day One. So then I bought a Ruby, size Medium. Seemed to work, but I woke up every morning with a wide trough dug into the front of my scalp, from left to right, followed by headaches.
Next was the highly recommended Respironics Premium Chin Strap. Useless - either too loose and did nothing and kept sliding around or just tight enough and gave me another dent in my head and headaches and sometimes a very scary sharp head pain during the daytime.
Finally decided what I needed was the Papcap. It seemed to make sense - spreading the tension evenly all over my head, not trying to wrap a belt around a bowling ball etc. etc. First few nights it was just loose enough so that it kept sliding down over my eyes; tightened it up as little as possible and back to big daytime headaches from the nighttime pressure on my scalp and brain!
That's when I began to get worried about the resultant head pains and began to wonder - Is it really a good idea to sleep 8 hours a night with a tourniquet wrapped around your brain and all the blood vessels in your head?

So I think I've sworn off anything that requires putting any tension or pressure on the top of my head.
Somewhere along the way I also tried chin-up strips and also fully taping my mouth. Result: a sense of panic and helplessness in my sleep, and lots of challenge every morning trying to carefully get the tape off my mustache and beard without painfully tearing the hairs out. Nighttime hostage in a bank robbery, torture victim in the morning.
My current effort is the soft neck collar discussed in another thread recently. So far it seems to be working reasonably well. Leak chart not perfect but acceptable. Still need some sugar-free lozenges for dry mouth but nowhere near as many as with the chinstraps when they were not cutting into my head all night.
Regards, Nate