Glad it worked well for you Tony, I think it might've worked even better if I'd remembered better & explained a bit clearer than I did earlier (bear with me the old brain cells ain't what they were)
With sports like wakeboarding, cycling & long jump I like to use just a single point because the athletes faces are rarely on the same plane of focus as their bodies when they're making their big effort which as you know is a big problem when using long lenses at or near wide open, especially when you're filling the frame well. I tend to use a single af point at the top of the grid & focus on the face if possible.
With cycling a good target is the front of the crash hat because quite often they have bright colours & those air cooling flutes, if you use surrounding points af can often flick on to the riders shoulders where they normally have all kinds of high contrast lettering to attract af. (incidentely I've had good results with lesser af by setting a centre or with surround point and focussing on the handlebar/stem area which when they are travelling towards you is more or less on the same focus plane as their faces)
With long jump (sitting at the end of the pit with a 300 or 400) if you are focussing on the athletes body during the run up focus won't be far off their face but as they jump they put their legs in front of them, using single point with surrounding points the tendency is for af to flick to their feet & unless you're shooting an advert for Nike trainers (other brands are available)
it's not really what you want, so in the past I've always tried to keep a single point on the face, very difficult because they're not exactly keeping their heads rock steady as they take off, fly through the air & land.
I now remember how I was shooting the wakeboarding. I'd been trying to use a single point at the top of the grid on their heads to keep faces in focus, everybody try it some time it'll send you to the loony bin unless you're better at it than me (not hard) I found it practically impossible with all the spinning & somersaulting they were doing, & had a very poor hit rate when looking critically at the sharpness of the faces because most times af had grabbed onto the highly contrasty wakeboard decals as they spun around. That's when I thought I'd give this iTR a go.
I told you earlier that I used the centre point in the full 61 points grid to initially pick up focus, sorry that was a mistake, when you enable the full grid you can shift the single focus point around & put it where you want so I put it at the top of the grid. As the athletes make their approach before they do all the fancy stuff I put that single point on their heads, I think it's important to establish a good a lock as poss. at this stage & track carefully for a second or so, once they start all the jumping, somersaulting & other lunacy that I can only be in awe of, let the iTR do it's work. I could see an immediate improvement, you're never going to get a 100% every shot in the burst pin sharp focus on the face in this sort of sport when using long telephotos but the hit rate will improve enormously I found.
I personally wouldn't use or have tried iTR on sports with more than one competitor in the frame so don't know whether it would work or not.
Stew
:nono:
..I ahve had at least 4 or maybe 5 done over the yrs under warranty..there not covered if you get an extended warranty on top...the topup warranty canon where selling.. which is why i didnt buy one..
although some of them were 
shots.