Problem with a tree like that is that there isn't consistent enough holding wood for a predictable drop -- no way to get a reliable notch or hinge. I guess I'd spend a lot of time trying to determine if there's enough wood for a notch in a falling direction that would work, and go from there. If not, I'd probably put a rope on it as high as you can, take up the slack, and then bore it out carefully so that it goes over in the direction of the rope when tensioned. So instead of creating a notch and then back cut, you're pretty much just doing a back cut to relieve tension fibers. But this is all conjecture -- I'd really want to examine that tree on site to really recommend an approach.
Last time I did a tree that was a little worse than that, I pulled it over mainly with rope/tractor. I used very minimal sawing to nibble away at tension fibers at the back of the tree, gave a pull with tractor, then slackened the rope, nibbled a little more with the saw, then gave a pull, etc, until the tree went over. If I recall right, it took about three "iterations" of this procedure until the tractor could pull it over. I wouldn't have wanted to cut too much since it could have caused the tree to rotate or fall over in an unknown direction by itself. So I basically kept nibbling at the back fibers until just enough had been cut that the tractor could pull it over, but not so much that the tree rotated/fell by itself.