I've had my machine coming on 2 years and I've always had this issue because of 1)I was born with fused vertebrae in my neck and 2) I have some nerve damage in my neck due to small injuries say while skiing, falling off a ladder, little things like that. Anyways, if I tighten my mask so it's snug, I get tingling in my arm, my neck hurts immensely, I have headaches but it just hurts so much I can't tighten the mask tight enough to sleep throughout the night, it's almost as bad as no CPAP at all, but that's not an option since I stop breathing 90 times a minute and my pulse ox is 45 while I sleep. So I roll up a facecloth now to put under that back piece and today I'm going to Joann Fabrics to find some different foams to try to make something that will be even better. I know I can figure it and if I do I'll take a photo and post for you all.