This is how Roan sleeps - curled up, butt in the air, arms tucked in like a turtle.  I now understand exactly where "childs pose" in yoga comes from.
Note he is wearing my undies circa 1977
Lula used to hate being on her tummy and would immediately roll over onto her back, although she didn't really like being on her back either.  Then one day she was fussing and I put her in Roan's turtle tuck and she zonked out immediately.  However, it's impossible to get to her G-tube when she's on her belly so we put her on her side and prop her with so many sandbags it looks like we're protecting her from a flood.
She's sleeping in the buff because it's already hot as hell here.
This is exactly how I slept when I was pregnant. Propped up with countless pillows and blankets; the poor man's zero gravity machine.

Of course, we're all so tired around here that we will sleep in just about any position if given the chance.