7D Video with a Canon 300 2.8L IS ll
Are you going to shoot at max aperture? effectively f5.6? Too bright for daylight at video shutter speeds (that is typically 1/60th for NTSC, 1/50th for PAL) so you'll need filtration. A polariser is a good start as it may also help your sky in some situations.
You are going to have effectively 1000mm of lens (well 960mm) which is going to reveal every single flaw in your camera movement. I would be looking at a sachtler ACE for this kind of rig, although the 300 f2.8 may well tip the spec'd weight. Something like a manfrotto 504 HD head?
With weight on tripod hook.
I would try the lens on it's own and see how you get on.
Apart from the movements there is also the issue of ramping at the end. Are you going to let the plane come into shot then track, and then fly out of shot, or just track and cut between movements?
You are going to be doing very well to get the camera framed and tracked in video with this set up. I would use the 300 on it's own, and would just use the LCD to give you more space to move, also it is easier to find and track with one eye away from the camera. LCD makes this easier.
When I've shot at airshows before I've used a conventional ENG camera with a servo lens, start wide with focus just shy of infinity, find and track the plane on wide then servo zoom is far as the lens will let me, tweaking focus as I reach the end of the zoom.
This is diffiuclt on SLR's but not impossible. Push pull zooms are actually quite useful in this regard, something like a 28-300 L or 35-350L is ideal, moderate wide angle, decent tele, the 100mm-400mm is usable enough too, obviously stop down before zooming to keep the constant 5.6 or whichever aperture you want to shoot at.
This is one of the areas where DSLRs fall down. I see them as a weapon in an arsenal. Not a one size fits all solution.
Whats often forgotton is that with a stills camera you only need the camera to be in focus and well composed for the photo you end up using. For video the quality has to be contiguous.