From memory (and I'm going back over 25 plus years) the adjustment on coilover shocks is not designed for height adjustment (although I am always willing to be proved wrong!) but to adjust the preload of the spring which in turn stiffens or smooths out the ride. The springs have a spring rate curve which allows at "normal" adjustment to take bumps without being too harsh, yet progressively gets stiffer the more it's compressed. Therefore, by lowering the bus by slackening off the springs to allow the bus to settle lower will effectively soften the suspension, as will compressing the springs to raise it a little increase the harshness of the ride. This will need to be balanced by the adjustment on the dampers to effectively dampen the change in spring rate. i.e. too harsh a spring rate and too soft damper setting will have the bus wallowing after a bump
So the point of all this rambling, which could be complete cr*p (memory isn't what it used to be!) is don't set the ride height by the coilovers, set it by the rack height adjustment, and tune the ride comfort by the spring adjusters in conjunction with the damper settings
Hope that's helpful?