Chris,
The bad news mate, is you can't move it. If the chain's tensioned correctly then that's it.
From your diagram, Ducati Leeds haven't actually got it wrong. 4.30 to 5 o'clock is just the "ideal" position. The most important thing is that the horizontal centre line through the axle is below the horizontal centre line through the eccentric.
What size sprockets are you running? If you've gone up at the rear then it's possible a new longer chain is in order. Adding a couple of links to the chain would probably put it all where you'd like to see it.
Hope that helps, Neil.
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