I have a stump grinder for the PT and I also had a Ventrac stump grinder that the dealer showed me a demo on. Basically, you start grinding at the far end of the stump and only turn left and right until the stump is chewed away at that point. Then back up a couple inches; left and right again until your at the other end off the stump. So, your just taking off a small layer, then drive forward and take another layer off. Your only taking off about 3/4 at a time with a smaller machine. An ash tree stump I just done and could only remove about an 3/4 in a swath. Another thing, the visibility is always lousy, so I learned to cut the stump by feel. If your taking too much off, you値l know it! There痴 a fine vibration that goes through the machine when I知 at the right depth and speed of turning the machine in the left /right direction.