Several people have asked how we reengineered the side gaucho's support system so that it could extend to 52" wide (standard double bed width) instead of the original 47" - so here is an overview of what we did.   This is much more comfortable for two adults.  This does make the isle a bit narrow, but it is still very passable if you walk sideways.

Support Detail (see pictures below):
The original extension system as used by Airstream used a manufactured product designed for extending kitchen tables for adding additional table leaves.  This was not very strong or rigid.  It was an inexpensive solution that used available parts.  In this design, each wood extension rail has a dovetail routed down its center. There is a small fitted wood piece glued into the end of each rail that slides within its partner rail, and a floating spacer to prevent over extension.  This rail design puts all the load through the small wood pieces and transfers it to the upper portion of the rail. This system works OK if the rails are not extended very far, but would likely fail by splitting (either the small wood piece or the rail) if over extended. Any slop in the fit results in sagging at far extension.  (It is sooo much easier to do a physical demonstration than to provide a verbal explanation!)

The system I devised uses three sets of extension rails (just as Airstream did).  Each set has two fixed rails solidly mounted in the frame of the couch.  The  rail that extends slides between them.  There is a metal plate bolted between the two rails (on the bottom) where they come out under the front edge of the couch.  Picture 1 is looking up from under the front edge of the couch.  The sliding rail has a metal plate bolted to its bottom as far back as possible. This plate slides against (and transfers the load to) the two fixed rails.  Picture 2 is from the inside the bed frame looking up at this detail.  Picture 3 is the top of this detail.  All of the rails are made of white oak (a very strong wood and the same material as the original table rails).  Other hard woods would work but are not as strong.  They measure 2 1/2" by 3/4" thick.  I used 1/4" aluminum plate - easy to cut on the table saw and to drill.  Steel would also be fine.  Bolts are 1/4" and pass all the way through the rail to blind nuts on the top side (this transfers all the load through the wood).  There should be about 1/16" to  1/8" slop between the rails.   Alignment is critical for smooth operation. This system allows the front edge of the couch to be lifted up (as much as is needed) to clear the stops that hold the couch in (in the retracted position).  Sag is negligible at any amount of extension.

Cushion Detail (see pictures below):
Picture 4 shows the cushions in the retracted position with the back (detached from Velcro on the bolster) and lying on its face. All three cushions are separate. The lower cushion extends under the bolster to about 2" from the wall. Picture 5 shows the bed extended with the back cushion ready to slip down between the bottom and the bolster. The back cushion has to be flipped end for end for the angles on the edges cushions to mesh correctly.

Picture 6 shows the bed all opened up and ready to use.  The approximate size of each cushion is as follows:
Seat 30"
Back 14.5"
Bolster 7.5"
TOTAL width 52" 
It is MUCH nicer for two to sleep on than the original 47" width!  There is still enough room to walk sideways along the isle (about 8 3/4" in front of the refrigerator and about 11" in front of the cabinets) with plenty of room for your toes to fit under edge of the bed as you walk through.

Back support (see picture #4) attached to wall 5 1/2" 
Between the bolster and the back support we put our sheets and  some of our other bedding.  Perhaps a removable awning, or even a hammock bed if you have one of those would fit here also.

Picture 7 shows the goucho made into a couch

There are many details and measurements that one would need to have or to work out before actually constructing the bed.  Hopefully this information is enough to give you a general understanding of the concept.   If you see us at a vintage rally (we try to make the ones in California) we would be happy to show you the actual construction.