When I rebuilt the pull out couch/bed in our Globetrotter I went with the 3 section slides illustrated in the link above.
They made the pulled out bed feel more stable than the originals. With less flex there was less of a tendency to have the feeling of rolling out of bed than we had with the originals.
I think I got mine from a Rockler woodworkers store, but, that was 10 years ago. The price was reasonable and they were in stock.
AirForums # 2806
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Not All Who Wander Are Lost.
Avid supporter of trailing edge technology.