Spot on Lorne, They have to be tight enough to not self tighten further, This gives a predictable pressure to release them! But also protects the splines of both elements. And it's the length of bar that gives consistency of applied torque, Mainly to the maker but will achieve fairly similar for most normal users. I have a six hundred mm torque wrench. the same length almost that I fashioned my home made spanner to. I also have Lionel's socket and this was how I found the length I needed to apply the torque I decided I wished to use, Not fair to share this I think as It's my choice but I'm sure if you try something 600mm long you will find your choice too.
Just a point of interest: I don't have a limited slip diff and find that the rear right wheel is the culprit for self tightening.
