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Have you turned "Just Scan" to "on" rather than Auto? This eliminated any overscan completely for me. Go to All Settings -> Picture -> Aspect Ratios -> Just Scan -> Set to "On". You might need to do this for all HDMI inputs you have connected.
AHA That did the trick! Thank you very much!!!
Yet another reason why LG overhyped the PC monitor credentials for this (or at least as released) - is there a full "getting the ******* thing working like it should" guide anywhere yet?