Re, top bunk sleeping comfort, or lack thereof:

  First effort- a cheapo $10 worth of egg crate foam, purchased at
Building 19. (DB understands) worked well.

  Subsequently, an inch and a half IIRC of memory foam found at
Tuesday Morning, $20, works even better.

  In each case, trimmed widthwise, and cut to fit underneath each
cushion separately, making it easier to get the bed to fold.

  A double fitted sheet lives on top of the mattresses, and in the
nonexistent space at the rear, stays my summer rig, two fleece
sleeping bags zipped together, and down pillow.  All squashes nicely.

George/ATL