As a young person in an old persons body, and a side-sleeper, I also need something to wedge between my knees much of the night, so the backpack-buffer is very useful. Can have issues with touching the walls in a snug/shared tent tho.
@BortEdwards Yep, that's shelf liner, sold in a roll at Walmart, Lowes, dollar stores, etc. It's extremely handy!
I actually put dots of seam grip on both sides of my sleeping pad, not my tent. Now not only does it stay in place, so does my sleeping bag/quilt! I was literally slipping off my pad and would wake up scrunched against the wall of my tent. lol