Hammock wouldn't do it for me, I don't think. Since my van isn't insulated I figure I at least deserve a super comfy bed.
From the bottom up......
MDF support running 4' of bunk length.
MDF base/board 72"x36".
2, 72"x72" furniture pads folded in half.
72"x36"x6" (twin) air mattress.
Queen comforter folded in half (padding).
Twin fitted sheet over folded comforter and air mattress.
Twin flat sheet.
Twin comforter.
Pillow.
Of course, beside it, is my Wally World lounger that I like for move watching and naps on warm days.