Seems like a waste of time to me. Just make sure the spur gear doesn't turn at all, when holding both tyres and trying to turn spur gear by hand. That would be the minimum tightness. From there just adjust to suit. Make sure you recheck from time to time, especially after a rebuild, as the diff does loosen up a bit.
A slipping diff is a nightmare in my opinion, as it always means slow acceleration, too much corner entry steering, and understeer mid corner/ext.
Mike