Mike...
A 300mm will suit most locations. Although I used the 1.4tc at Cad West is was probably too much. I had to stand right up the top of the hill and when the planes flew through I couldn't get them in the whole frame, but I decided to use the 1.4TC to capture them as they approached, the first GR4 was shot with the converter on. Its always nice to have it, just in case you need to draw them in that little bit more.
1 Zulu Alpha...
Thanks for the comments. The sountracks are by Amy MacDonald.
Mark