after greasing my bearings, i put the castle nut back on finger tight and the hole for the cotter pin does not line up with a slot in the castle nut. should i back the nut off or tighten it past finger tight to get the hole to line up? tightening it would probably put about 5-10ft.lbs. on the nut

 

Turn the rotor as you tighten it, to about 15 ft-lbs on the nut; then back it off; then tighten it to about 10 ft-lbs while spinning the rotor, then continue tightening it until the holes line up.