1947 fork seals and holders

[hatrack]

Assembling my forks today with new bushes, seals and seal holders, I found that fully tightened there was a gap with threads showing, of 2.5mm between the top of the fork slider and the shoulder of the threaded seal holder.
I could fit an "O" ring to cover the gap.
Or I could trim 2.5mm off the fork holder.
Or 2.5mm off the top fork bush.
Or is there a slimmer oil seal available?
All parts were from the club spares scheme or Classic AMC Spares.