You will need to use whichever spacer or combination causes the cassette to stand 1 or 2 mm proud of the freehub, so that the lock ring clamps against the cassette and not the end of the freehub. If the rivets (or screws) at the back of the cassette cause issues you can just grind them off or remove them, they are not needed after installation and only serve to hold the assembly together during handling.