Start with level ground, how do I adjust a box blade to cut at an angle to create drainage swales? Shorten one of the side arms of the 3 pt hitch? If so, then would the side with the shorter arm be the bottom, "cutting" side or would it be the other side? Hard to visualize. Again, start with level ground, how would I taper the whole thing to drain a certain direction? Put the box down at the desired "low" end and pull toward the "high" end?? Thanks for any help!