Just acquired a new 7D. I am keen on photographing Birds in flight. When I had my 40d I put all the focus points active as it was extremely difficult to follow a bird using the central point. Now there are other options: single point with expansion or zone AF. I am off to the Far East soon with an opportunity to photograph Kites, Eagles and others ( a Storm Stork...??). What would you recommend? (AI Servo taken for granted)