Notch it the way you want it to go and use wedges. I just cut down 11 that size on 5 acres we just bought. Had an oak tree fall backwards on a Kubota one time trying to use loader to push it. if you are dealing with an 80-90ft tree, pushing on it 10ft high you are putting way more pressure on the bottom than the top. Cut to close to the notch with all that pressure and the bottom can kick off the side the notch is on allowing tree to fall on you and tractor.