Last time I brought a big one down, I just took one of my M9000 Kubota's, raised the bucket up all the way and pushed it over (after cutting through about 3/4 of the way). A 10,000 pound tractor works real well.
I got into a lot of trouble doing that one time. I managed to extract myself from the tough place, but it was definitely a learning experience.
I was working out a row of cottonwood trees that had grown tall and were all prominently leaning over the highway right-of-way fence. Sez I to myself, "it'll be easy to push those leaners back the other way."
Boy was I wrong. If you raise your loader frame up nice and high so as to get the most leverage on your tree, you can change the dynamics of your loader so that the loader pushes up more than it pushes forward. This of course depends upon the length of your wheelbase and the height that your loader reaches.
At the decisive moment, I discovered that my tractor was driving under the leaning tree, compressing the rear tires into the earth while the front end was being lifted up by the rising trunk faster than the tree was being pushed over. This discovery came too late to escape, as my tractor was now trapped under the tree and the trunk was down to hinge wood.
I ended up setting a rope, tying off to a pulley on the guardrail about 80 feet uphill, and then pulling the tree over with another machine.. I pretty much don't ever rely on pushing a tree over since then, unless I know for damned sure that the machine outweighs the tree.
If nothing else, a tied-off tree won't fall on your machine when the plan doesn't work out right.
EDIT: Your machine has a 90 inch wheelbase, and a nice tall 133" height to the bucket pin. Raise that all the way, push hard on a leaning tree, you will have done the same thing that got me in trouble. When your bucket height is greater than your wheel base length, pushing a leaning tree over might cause the point of contact to rise faster than the tree pushes over. All of a sudden, you discover that you are driving under the tree forcefully while you tractor's front end goes up more than the tree does. You are now trapped under the tree, because you won't discover this problem until the trunk has been cut most of the way through.
Perhaps this little sketch will help you see the dilemna I put myself into:
Furthermore, this technique of pushing over a leaning tree can put vastly more force on the hinge wood, because the leaning top is heavier than the trunk beneath your push-point. When that hinge wood breaks, the trunk comes up and the top crashes on your tractor.
Solution: If you feel that you must push it over with the tractor, be sure that you set your bucket low enough to compensate for the rising point on the trunk of the tree as you lift & push it over against the lean. If that lower starting point exceeds the strength of your tractor, try another method.