Final update. 3 shims on the rear is still enough to give me workable elevation. 45 inch pounds on the mount screws and centering them on the dovetails, as per instructions, forced windage straight enough to work with. The scope appeared to move freely before I clamped the rings together, so don't think it's pinched anywhere.
I've never had these sorts of issues. Not sure how else to approach this one, so think I'm calling it good enough and done.