Creating upper storage is not that hard, see here:
http://picasaweb.google.com/starwagen/UpperStorage
Upper bunk comes out with four screws, easy to store, easy to reinstall.
Some people have used plastic storage boxes in the area.  I did that for a
couple of years but like the current setup better.
You have about 5 1/2 inches of clearance with the bunk out.  The wood used
for the storage compartments is finished 1/2" x 6" that is 51/2" wide.  Held
in place with small brass 'L' brackets and small screws.
If using plastic storage bins you need to to provide something to keep them
from sliding out, Larry Chase of Phil Zimmerman can post pictures of the
bungee cord setup they created.