That's weird
With your model year and the measurements you've quoted, your slave should definitely be fitted with the 10mm spacer. But the symptoms you describe sound like something is preventing the clutch from engaging. You could try refitting the slave without the spacer, just to see if that makes any difference. I'd also withdraw the pushrod again just to check it's still true (if it's been put under undue pressure, it may have been distorted).
If you still have problems, give Oberon a call. Nick recently had a problem with his slave and the boss, Steve Street, was very helpful (turned out to be an assembly error at the factory).
http://www.ukmonster.co.uk/monster/s...ad.php?t=58107