From experience, here's what I can fit behind the folded front bunk
section up in the loft.

   First off, I've put a layer of 1/2" memory foam cut into two
sections underneath the mattress pads, and this has made a great
improvement in comfort.

   Behind the folded front section, I store 2 zipped together fleece
sleeping bags, one extra fleece blanket and my pillow.  I should add
that there's a rain fly tied to the top braces in the front that nests
behind the cab storage tray.

   If everything's situated properly, the top will close with just a
small amount of extra effort, and the front seal should mate up
tightly all the way across the edge of the storage tray.

   Every once in a while it'll lift a skosh on the driver's side,
whicht means that I was in too much of a hurry arranging my stuff.
If that seal isn't tight and you don't notice it right away, you'll
probably hear air infiltration it as you drive.

  Next time I open the top, my pillow looks as if it's been in a 40
ton press, but it fluffs right up.

George/ATL
in North Beach, Burlington, VT