A couple of years ago I cleared about an acre full of oak and chinese tallow. Some of the trees had trunks up to 16 inches diameter but none were more than 25 to 30 feet tall. On the largest ones I did a circle around the tree with a subsoiler to cut as many roots as possible. I did the climb the ladder thing and hooked a chain cinch about 10 to 12 feet above the ground. I then used 40 feet of chain to the drawbar of the tractor (never hook above the axle). To protect myself as much as possible I hung a weight on the chain half way between me and the tractor. I also mounted some horse panel to the roll bar (which I decided to keep in place for mowing and other things) Horse panel is made up of 1/4 inch steel rod with a 2 inch by 4 inch pattern. I cut it to size and clamped it in place on the back of the roll bar with large hose clamps.