Six concrete deck base blocks were enough to drop down the back of the wagon significantly. Don't know how much each weighed. Just put enough weight in the back to see the suspension drop visibly. When the engine is started it should level out. The best way to tell is to keep your left foot on the ground when starting the engine. You should be able to feel minute changes in the suspension in that foot. It probably should take about 30-40 seconds(?) to raise it up.
It's not that hard to work on the SLS so if it works at all, I'd be happy with it.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13