I shoot figure skating with a 5D3 and a 70-200 f2.8L II. There's a lot of erratic motion with change of direction and varying speeds. Sometimes there's a single skater, sometimes several. Case 5 is supposed to be for sports like skating, but I find that Case 2 is more effective, especially if there are several skaters and I trying to get shots of one in particular. Case 2 is better at staying locked on the skater when others get in the way.
I also shoot single point with 9 point expansion and AI Servo. When using expansion with Case 2, the key is to lock on your subject with the center focus point. The surrounding expansion points will then help stay locked if the center point moves off the subject.