I sleep primarily on my side but I toss and turn a lot (back pain stuff) and I don't have a problem with the P10 moving out of my nostrils.
That said, maybe a different nasal pillow mask would be more stable for you. One of the negatives to the P10 is that it maybe isn't quite as stable as one of the other nasal pillow masks but I am okay with that because I prefer less on my face and head and will deal with a little instability to get the "less on my face" thing.
Have you tried some sort of hose management system to help with the hose tugging on the nasal pillow frame?
If you haven't I would suggest starting there because it can be done easily and cheaply with usually something laying around the house.
See this for ideas
viewtopic.php?t=10640
If you want to try a different nasal pillow mask...maybe look at the ResMed Swift FX nasal pillow mask.
The hose swivels and the headgear is more adjustable. I used it for a couple of years until something else came along that I liked better which was the Tap Pap...then the P10 came along and I started using it.
The Tap Pap uses a mouth guard to hold the pillows in the nostrils and routes the hose naturally over the head with no headgear at all.
So that was definitely covering the "less on my face" preference.
Those nasal pillows never moved out of my nostrils no matter how much moving around I would do.
I sleep in all positions and the nasal pillows rarely move. I don't use a special hose management system other than where I route the hose on the bed....it lays on the mattress and goes up around the bed pillow to come down to my face...so it is sort of overhead and thus I don't have the hose dragging on the mask.
The P10 hose doesn't swivel like the Swift FX and while it wasn't a deal breaker for me I can see where the swivel is a definite advantage.
I may have to RISE but I refuse to SHINE.
If you want to try the Eclipse mask and want a special promo code to get a little off the price...send me a private message.