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First, confirm all of your springs curl up when the sub-chassis is unhooked. Then you use the rear nut to bring the sub-chassis high enough to float between the lower and bottom stops. Then tweak the three nuts to ensure the platter is level but not necessarily even with the top plate. If you then need additional height, you can loosen the locknut on the center bearing and raise that as it is threaded. You will then need to make sure your arm cued-up position will still clear the record.
As to centering, there is some side play in each leaf spring and you can also get some side or front/back play by slightly bending the rear height screw. I have never seen the need for more than 1-2mm of adjustment. If you do then look at your top plate alignment as that is likely out.