I also changed out my OEMs for these Ranchos.
The brochure I got with mine suggested 6/3 for highway, 4/4 for Off-Road.
Mine starts to wallow/bounce too much if I have the fronts lower than 3.
I usually keep them at 4/4 or 5/5 as I go on dirt/rocky roads daily.
Other owners have said that EVEN AT 9, these are still softer than the OEMs. I agree.