I went a slightly different route and skimmed a "shoulder" on the two spacers that go under the cup bearings in the hub.
I reckoned I could cut some metal off there and not weaken the spacer much. It only needed 1mm depth of cut to clear the inner ridge in the hub and let the spacer slip down to the correct level. Now everything fits very neatly. I haven't taken it on the road yet.
