Nikon D300s AF area for birds in flight

I am using a Nikon D300s for bird photography and was wondering if anyone in this forum is using this camera as well. If so which Dynamic AF area setting are you using for best BIF results...21 points, 51 points or 51 points 3D tracking ?

I have the D300s and I've used 21 and 51... I have tried using the 3D tracking but find that it doesn't work that well with birds in flight as it often focuses on parts of the bird that you may not want in focus. I believe 21 works the best - but it also depends on the lens... I use a 300 f4 + 1.7X TC most of the time and AF is slow to begin with so I dont' want to overtax it with 51 but with some of my raptor photos when just using the 300 f4 I have used 51 to decent success. Take a look at my gallery to see

Thanks Luke for the information !!

I tend to agree with Luke,
The less work the camera/lens has to do, the quicker it will do it.
With BIF you really just want the AF to concentrate on your prime subject.