One thing I have tryed in the past at a Kite feeding station (in scotland) is that if the light conditions are stable then meter on some grass ect. then use the settings in manual, this helped get an even exposure against the sky,
When there has not been as much opertunitys, I.E. away from feeding stations then use AV, and tend to set it at around F9.
Hope that is of use, but must stress I am no expert.
Ok thanks, I'll give it a try
Thanks Tom, did you find the 300mm had enough reach?