Doing your front cross outside the box, in example 1, takes the off course jumps out of play. Ideally the cross should be done at the far wing of the jump, but anywhere along the blue line will be giving the dog directional information. Derrett would run inside the line of jumps to the finish, as he wants his dog to know immediately that if he is on the other side of the jump that it is a serpentine as in diagram 4. However he explained that this is a choice he has made, not to 'layer', and admits that the decision cost him the world championship, but the time saved by not having to do the false turn in diagram 4 pays off more often than not.
Doing the front cross inside the box, in diagrams 2 and 4 again directs the dog to the correct jump, but doing it along the blue line, and if possible at the far wing, also lets the dog know early the direction in which he will be going. Doing the front cross in the middle of the box will turn the dog away from jump two, without giving immediate information about where he is going.