Good shots! No substitution for length when shooting birds. I picked up a used 400 f2.8 years ago. Even tho its a heavy bugger for me now I keep it for those times I want to shoot some flying buddies. I have to put a 2X or at least 1.4X on it and shoot on a tripod.
That 400 f2.8 is a great lens as well. Have you tried a monopod instead of a tripod?
I did shoot it with a monopod years ago when I shot high school football. Never could get comfy with that setup even after many hours of trying. Ended up using a Wimberley, even for shooting air shows.
