Adrian,
The height of the camera does seem pretty vital.
Did you experiment with the height of the drone/camera during the filming process?
Very high isn't too bad, as it gives a good overview, but at middle height curvature seems to be more involved and a hole looks like it runs along the top of a spine/ridge. There is some footage at head height, and head height does vary, but I'd be interested to see sample holes just filmed at head height.
Atb