For support of the cantilevered portion we used 2 pair of 24" full extension drawer glides, each pair rated at 220 lbs so no legs required. It has not sagged a bit and I'm no featherweight.
I stole the mattress spec from David of Conifer, CO, aka "dbj216". His 4" mattress had a density of2.8 pounds and firmness of 36 Indentation Load Deflection. We gave this info to our upholstery folks and they may have tweaked it further. Jane adds a 1" dimpled soft foam pad on top of the cushions so she does not notice the joints between cushions.
David and others were quite helpful to me as the renovation progressed.
To see how this was framed, go to page 7 of "Jim + Jane's 1967
Safari" blog below your posting.
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