Alright my turn: )...
Burbs, true, loosening a diff screw after it is fully tightening is bad as you might break the diff bolt-I know I've broke a shet load of yok diff bolts and yes I can see where tightening a diff bolt too tight will leave pitts the naked eye cannot see but affects performance. It's best to tighten the diff up untill it cannot slip by hand while holding both outdrives. The niftech tool can be used two differant ways that I know of and that is 1, use it to fine tune two diffs after you've tightened them both up to where they don't slip by hand and 2, Use only the tool to rebuild or assemble new diffs. Both are gonna get you in the ball park.
Now the tool just needs to be digital reading down to the thousandths...: )