Greetings Rick and Keith!
My '64 Overlander was originally equpped with the Hammock Bunks - - one over each of the center twins. Unfortunately, these were separated from the trailer between when its original owners sold it in 1980 and when I purchased it in 1995. I remember sleeping in one of these hammock bunks in 1964
(I was five years old). It was basically an aluminum frame (very similar to an army cot) to which a canvas material was attached. The aluminum frame rested on "L" shaped brackets on the outside walls and there was an aluminum rod that slipped into a special bracket mounted in the ceiling at either of the interior corners. The hammock bunks folded up and were stored in one of the wardrobes at the rear of the trailer when not in use. The biggest drawbacks were that they were not to be used for individuals weighing more than 90 pounds; and there was also rather minimal clearance for both the occupants of the fixed beds and the hammock bunks - - this could be componded today if the owner has retrofitted the coach with innerspring mattresses as I have done.