My two cents..... aside from the current arguments. You might try putting the camera's tilt and pan on a seperate radio. Nothing fancy, a bargain 4ch Futaba with analog trims will do. Y'know the radios everyone is trying to get rid of? You'll have a pilot and a camera man, each on his own transmitter. I think it'll improve the shot too.

Also, a good idea already stated was hire a seasoned pilot for the filming. Give him credit in the film and the plane when you're done. I'd do it for the plane!

If you won't mind the noise, a nitro or gas motor will be cheaper, better and longer flight times. The vibration can be isolated. Balance the prop, bushings on the motor/mount and isolate the camera from the airframe through bushings. I'd think all vibration could be removed.