I can remember having to torque the castle nut up to a certain value, then turn through a further 90 degrees. If the split pin holes don't line up, slacken the nut slightly rather than tighten further. Does this not apply any more?
The bearing is not a taper bearing dave it's a solid roller bearing, which will have torque setting but we tightened them up with the gun or till tight by hand and yes slacken off till split pin hole lines up.
There is a washer underneath too, put a little grease on the splines of the cv shaft to aid refitting/removal.