BIF: Settings for 1d Mark II? Advice needed (1 Viewer)

I shoot with a 400mm f5.6 on the 1d markII. I get pretty good results. But for BIF's I'm not sure if I should use a single point in AI servo or use the option of activating 9 points / 11 points. Does the camera's auto focus slow down if I use the latter option? Is the focus faster with a single point? But then the single point focus is best with centre point and the centre point is not always where one wants to put the subject.
Welcome advice from the pros.

Not exactly a pro, but experienced. I still have my 1d MkIIn (same focusing) and 400mm f5.6 lens, although I haven't used the Mk IIn since getting my Mk III, the settings I used depended on conditions, how close and bird size for BIF.

A clear, uncluttered background and a small bird in the viewfinder and I would probably use all the focus points or the 11 especially for an erratic flying bird and to my knowledge, the focus doesn't exactly slow down, but technically a slightly, slower method as the focus point could keep changing as it tracks the bird. Bare in mind, using more than one focus point and the focus could be on the tail or wing for example where, ideally you want it on the eyes, particularly if photographing a large bird.

A more 'busy' background the center focus point has a better chance of locking on and, since the one focus point is always (hopefully) on the target, it's faster although you could keep loosing the focus unless you are very good at keeping the bird center frame.

I found the best thing to do is just practice at all the various settings to find what works best for you under what conditions, since so many things can effect the result.

I never use anything other than AI servo focus anyway. With your servo tracking speed set to moderately slow. If it is similar to the 1DMkIIn, which I have, then that would lock and keep maintaining focus even while some distracting elements may come between you and the bird you're tracking.
I always use center AF point and usually have the surrounding (I think 9) points enabled too. Though center is all I need and suggest. I try not to get fancy with multi points, as then that will create more camera generated errors (possibly) rather than center AF point, in which case errors will be attributed back to you, the user.

Also, if you can, start using the rear AF button for focusing rather than the shutter button. That way you can also use the camera in a way as if you were using one shot mode, since you can focus with the back AF button, then recompose and take the shot. This is excellent for more static subjects (the recompose technique).

Ditto on everything Mr_Birdman posted. Excellent advice. Exactly what I do with my mkIV. It makes the job of getting better photos much easier, especially BIFs and action shots. Here's my article on the matter, with links to more information from others on how to do it - http://www.carolinawildphoto.com/backbutton_tip.htm