It seems a *very* tight fit – even without the central bolt I can only get the outer section halfway in to the top of the steerer tube (fork is a 2009 Revelation FWIW). I've tried putting it in the freezer before fitting, but it just gets stuck when the O-ring goes inside the steerer. Any suggestions before I give up and revert to a good old SFN?

Have you tried loosening off the wedge by unscrewing it with a hex key?

Check the post above, if it still does not work, with the bolt lose, give the outer section a little squeeze with a pair of mole grips, worked for me. Remember don't over-tighten the bolt when you do it up, been there done that, had to buy a new bolt, doh.

RTFM, no really do – I struggled until I actually printed the sheet and read it while fitting one.

just bin the o-ring. It won't miss it.

edit.. sorry, should qualify that a bit more. close it up so it expands a bit, so it will grip on the steerer. It should be firm to press in. Then it should have enough friction to tighten up and not spin.

Ta for the replies. I'd taken the wedge bit out completely and it still wasn't playing. Will try the mole grips and without O-ring though.

Yeah had same problem! Removed o ring and that sorted it!
Thanx Max