Sean, guess you know about how much you can take out of a tree's middle before it might set back hard. I might be skeered if there was a danger to something.
Its sorta like the quarter cut (half the backcut) technique for wedging little trees. You can remove one side of the backcut without the tree setting back, set a wedge, then cut the other side, and set a wedge.
In this case it removing the middle third to half, with a good depth, hinge to back edge of tree, of wood left on each side. When executed properly, its no big deal. Again, after setting the two wedges vertically, I should have set a wedge on the one side, then the other.
We tag team most trees, which I don't really care for that much, but it is how it is. Especially with big trees, wider than the bar, as there are different ways to chase the backcut around the tree. Duane rocks the bar tip back toward the back edge of the cut more than I'd like, and ends up close to or in the wedges time to time, or I have to wait to put in a wedge longer than I would otherwise.
If its a 40" tree cut with a 36" bar, I'd rather cut the one side up to the hinge, only 7-8" deep from the side, then cut the other side from the back of the tree to the hinge, dogging in frequently with little sweeps, or not levering against the dogs much. That allows as many wedges as desired without cutting off the tips.
Alternatively, I'll cut both sides up, leaving a backstrap. Prevents premature release, keeping the hinge fully even for tight shots.
Of course, with dead and/ or rotten trees, our forte, there is always an X factor. Knowing what decay fungi is affecting the tree clues us into what Might be hidden inside.
We usually would set a pull line close to buildings with a backleaner, but for some reason, the boss wanted to only take the pick-up with a couple saws and wedges, rather that the fully loaded bucket truck...and this was a park that is across the road from our shop, so saving fuel/ mileage was a moot point, essentially. For some (bad) reason, we don't have a throwline and bigshot head that live full time in the pick-up.