Sean
"Been there, done that" with that kind of shot and I know the feeling. Your assessment of the image is right on. Oh, if you had only had him banking a little and been able to get the head clear of the wing, it would have been even better. Your image can be posted larger here. I might want to add a little more room to the top and left....to give him some room to fly into. The bird appears very sharp but I believe that it is underexposed. You can brighten it up but you may also need to remove some noise from the BG.
This is gorgeous bird, so I think it's worth it to keep trying to get the bird to cooperate. Here is a little trick you can try to get a good flight image. Observe the bird from a distance to see if you can determine 2 perches it likes to use. Try to observe where the bird goes when it is spooked off one of the perches. Around here, it's usualy a utility pole and when a car drives by it will fly off and fly to the next pole. I position myself near the second pole and wait for a car to drive by. When the bird flys by on it's way to the 2nd pole, I get my flight shot. The key to this is finding repeatable patterns. Good luck!