More great shots. It looks like an extraordinary show!
For me, I think your shutter speed is just about right, for shooting from the ground. Your in-flight shots don't have full discs, but still have enough blurring to show the engine is running. I've seen shots with lower shutter speeds, and most of them seem to have a sharp area and a less-sharp area, and I think that's because the shots are taken from a fixed point and panning as the plane flies by, causing some areas to have slightly more motion than others.
I took what I thought was a great shot a few years ago, of two prop planes flying in formation, and I was trying to get as much prop blur as possible. The two planes were nearly next to each other and in a bank, and the placement of them in the frame was just about perfect, with one slightly closer and below the other. It turned out that I did get some great prop blur, but apparently I was tracking the farthest plane, as it was nice and sharp, but the closer plane was blurred because it was moving at a different rate relative to me as I panned. I decided then that I'd rather have more of the planes be sharp with less prop blur than the other way around.
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Ken Cartwright
No single drop of rain feels it is responsible for the flood.
http://www.techflyer.net