even with the spindle gripped firmly in a vice.
Have you tried to loosen the nut with the spindle clamped in the forks?
If you remove the disc, you should then be able to hold the spindle firmly by clamping the spindle with the fork caps, and with the wheel assembly
pushed all the way over to the right (timing side) that should give you enough clearance on the left (drive) side to get a spanner onto the nut between the hub and the fork slider to loosen it?
Be warned,
do not overtighten the cap nuts as the caps can crack (the torque figure of "25 ft/lb" given in some manuals for the OIF model forks is WRONG! Tighten them to 15 ft/lb.).
