1000km later with the RHS nut done up to 115Nm and still no click/clunk
If anyone has the adjusting cap and spring washer, it's pretty safe to torque it up in steps til the noise disappears.
Same axle is used in the plain nut + cotter pin models which take 185Nm according to the FSM. So the threads on the axles shouldn't get ruined with more torque. Maybe the nut.
You won't crush any bearings either, so no fear.
Just don't use a rattle gun.