Thanks for the info folks … I'll try to explain a little better.
Ok, the head tube with headset fitted is 120mm long. The thread on the steerer isn't long enough to allow the nut to screw down as far as is needed to clamp the headset. If I screw it down as far as it'll go (and pretend it's doing its job) I have a 30mm gap between the top of the nut and underside of the top crown, the steerer does reach the top crown … so, can I recut the thread on the steerer so the nut travels further down and use spacers between the nut and top crown as in stilltortoises picture (my spacers would be on top od the nut though)?
MaverickBoy surely the distance between the top and bottom crown is fixed as you can't alter the position of the bottom crown and the top crown / fork legs are tapered so the top crown will only go on so far … if I cut the steerer I'll still have my problem plus the steerer won't reach the top crown.
Cheers
Stuart