Doug. Yes -I almost always use Servo AF.
Yes - I almost always use the centre AF spot. Sometimes I've no choice as in when using a converter, as then the centre AF point is the only option. Much as I'd like to use the other AF points sometimes when I can, (no converter) in practice it's well nigh impossible as the birds are never still long enough, and you seem to spend more time changing the AF point than tracking the bird. The 500mm has focus lock buttons which enable you to AF with the centre spot, even in servo mode, but then recompose, when I can remember to use them and when there's time to still get the shot.
The spot metering is more tricky. Yes I do use it, but not all the time. Sometimes it can cause real problems in very contrasty conditions, in that you get the exposure on the bird right but if the background is very bright, spot metering just serves to blow out the background even more, so sometimes I find I'm better off using evaluative or average metering for a happy medium and doing the best job I can in RAW processing.
These shots were spot metered but as you can see there isn't too big a disparity between the birds and the background. If the birds were more in shadow, then you can see it may well have caused problems with the background.
Not a satisfactory answer really I suppose - I suck it and see on the day. :shrug: