Hello Jeanette and welcome to the Forum.
We have owned our 2006 SG from new and have not found anything to replace it with because it is so practical and compact.
You can find more information and photos on a previous thread.
Have a look at Modifications and Enhancements
Page 3, Modifications for Big Year Out- the Lounge by Chris & Susan
They have shown their very substantial mods for their purposes
I contributed to show how versatile the SG is on post no 339 22/1/19 showing our arrangement
Without checking on this cold damp morning I believe that the width of the bed at the body is 54″ and is 74″ long across width of van. The bed tapers into the feet (side bench seat) with use of the infill cushion .
This can be seen on the photos that I posted.
Fred