Hi Thomas,
As mentioned before, I worked in a Fiat Main Dealership back in the day.
We used to first tighten the hub nut to roughly 25 lb.ft while turning the drum/hub to settle the bearings (we didn't use a torque wrench for this, all Mechanics know what 25 ft.lbs feels like
). Then loosen the hub nut to where it's free and re-tighten it using firm hand pressure on a socket extension with a socket attached. (i.e. no ratchet or lever, just gripping the extension bar as if it were a screwdriver). This gives very light pre-load of the bearings. Then stake the nut in place.
There was a Fiat Special Tool for staking the nut - it looked like a large pliers/welding tongs and fitted end-on not side-on the nut i.e. it was used in-line with the stub axle. Inside one jaw of this pliers was a little pip of metal which staked the hub nut to the groove in the stub axle.These tools came in various sizes to suit the different Fiat models.
Oftentimes, the correct tool was m.i.a. so I just used a cold chisel with the cutting edge ground to a round edge. some others just placed a large screwdriver edge-on to the area to be staked and bashed it.
I never really liked this arrangement i.e. staking a nut in place. It means almost surely having to buy new nuts each time. I preferred what is used on other makes i.e. a castle nut and split pin, or alternatively a plain hub nut over which is placed a special cap, which is indexable to align with a split pin hole in the stub axle, plus a split pin.
I wouldn't worry about rotation of the wheel causing the nut to unscrew. I don't think this can happen as the heavy washer under the hub nut is keyed to the stub axle and would prevent this. I've even seen hub nuts barely staked in place, really just squashed a little using a hammer and drift (so that the nut could be re-used?) and these didn't come loose.
Al.