Some tech stuff...
Firstly, thanks so much for your positive comments, and I apologise for the delayed response...
John, I did the same at the Melbourne GP. There were just too many fences and no decent vantage points, so in fact, I'm not even going to bother to go back this coming year.
The bikes are slightly different. They are not as quick at the Formula 1's and I do in fact use the auto-focus on the 400 f/2.8. Generally, it is slightly easier than you would think. The most interesting photos are taken as the bikes are leaned right over in a corner, so their speeds are not that high and therefore the AF in the lens actually copes quite easily. As the bikes accelerate, obviously the harder it becomes for the AF to keep up, but at that point the bike is too large for the view finder anyway.
When panning from left to right, the speed of the bike is also not as great as it would be coming toward the camera, so again using AF is not an issue. Pre-focusing would not work in this situation I believe, unless you used a very small aperture in which case you would lose the bokeh effect. Haha !! There is actually a bit of trickery involved believe it or not. The use of a very large aperture does blur the background to an extent and gives you the apparent feel of speed. If you look carefully at any of the photos, you will see the background is relatively stationary. Unless you are an absoute professional (which I am not), I would hesitate using a shutter speed slower than 1/800sec. You may be able to use 1/400 with a smaller focal length but not with the EF400.
Shutter speed:
I have found, as with all of these photos, that 1/1250 to be about the fastest shutter speed to use, and not slower than 1/800sec. Any faster and you risk making the bike look stationary, and any slower you risk having a blurry image.
Aperture:
Using around an f/4-5.6 worked out well for these... most of the other pro's at the track all had 600 f/4's and one even had the 200 f/1.8, but they were able to get up right alonmg side the track...(almost).
Tilting the camera to the right also gives a fantastic perspective which is very useful to remember, and it is actually quite easy with the EF lenses by losening the thumbscrew on the lens.
Metering:
I normally use evaluative metering, but I found that 'centre-weighted average metering' to be perfect for this type of sports photography.
I also use a monopod, but as you can imagine panning is made extremely difficult with any kind of pod attached, (the 400 2.8 is a heavy sucker). Although most photographers use a monopod, there are alternatives available. One of these lens supports actually straps to the waist and I would imagine these would be an easier option.
I hope this helps John... I will look forward to seeing some of yours when you manage to take them.
BTW, the practice days are great because not too many people crammed into the good spots, and take lots of memory... I took 1500 during around 5 hours of practice...
Good Luck,
Regards,
Barry.