Thanks for the links to the pictures, RedThunder. Looks like a good strap to use across the front to stablilize a full face mask (or just about any type of mask, for that matter.) I've read of people using an ACE bandage or even a chinstrap that way...across the front and fastened behind the head. The strap you found looks very useful.
That's the same thing I do with the leg cut off a pair of soft, stretchy tights...placing it across the front of the Aura (Aeiomed's "Headrest") nasal pillows, the CL2 nasal pillows; down near the nasal pillows shell of the Breeze, etc. I also use it over the "simple cushion" of the ComfortLite 2 to keep that little nose covering thingy from leaking.
An extra strap across the front is often the one last key to making masks work. Works like having your hand up there lightly holding the mask in place all night.