GOL and all safety trainings I do we shoot for level at center of the notch.
This allows exact hinge thickness.Coming in above or below can look like you have an inch of hinge. but have less or more, depending on how the notch is placed. Having less can lose the tree to side lean or weight. Having to much can cause barberchair .
Couldn't agree more Dale, as in my previous post thats the reason I go to the extra effort to mark my back cut, I only fall trees on the weekend and I get a few odd looks and such but thats the way I was taught and I know my instructor fails proffessional tree fallers when he's doing audits for not having a straight even hinge.