Vince:
I don't believe Dents book covers the bore out the back method. Most would consider that the safest but I don't think it was in existence or widely understood back then. Dent's book did cover doing a face as far in as you could get it, making sure it was wide, doing two angle cuts that formed a triangle and they at least nipped the holding wood at the corners, then with your sharp saw cutting briskly through the remaining triangle.
Gerry Beraneck's (sp?) book; titled something like "Fundamentals of General Tree Work", also lists a Coos Bay cut. I have no familiarity with it but would recommend that you have both books on the shelf.
We had a pro cutter that I thought was the best faller/teacher I've ever seen tell us that while the bore was good, he never had a heavy leaner that the Dent identified method, (it actually dates from the X-cut days), above couldn't handle and that he was concerned with the bore method in larger West Coast Trees and bars too short with either method.
I would also suggest that there should be no wedging on a heavy leaner. That could assist a barber chair event, not prevent it. If you were to force the tree over early with wedges or have an untimely wind, either of those could contribute to the barber chair. You want to cut everything you can before it commits.
While working with a cutter on a NE Oregon fire this last summer, he cut a heavy leaning Larch with the bore method. It slabbed up the back just prior to finishing the cut. {Larch was used by pioneers for split rail fences and shakes-because of this splitting ability}. Not anywhere as dangerous as a barber chair, but potentially not good.
Another pro cutter told me of doing a bore cut out the back where the tree did a root pull just as he was finishing his cut. That root came close to grabbing him and pulling him toward the tree. This could be mitigated by cutting the root to stop this prior to the bore cut.
So while you should regard the bore out the back as the best, please be aware of what a complicated world falling is.
The escape path from any potential barber chair is of extreme importance.