Can I ask a related question. Graham, I don't want to hijack your thread so tell me to go away if you feel I am.
I'm a new D7000 user. I occasionally shoot cycle races. Typically this is either pretty much head on or head on but to the side a bit. I don't usually try and capture straight across eg left to right. Speed of riders perhaps around 30/35 mph. Riders wearing different colour clothing but team members may be grouped together at times.
I'd planned to shoot in AF-C either single point or 9-point. Does that seem to make sense?