G-SPOT,
The Eclipse has plenty of tail. The CG envelope was restrictive on the early aircraft due solely to trim tab effectiveness. Even then, you could only get that far aft when you're single crew with a very light weight pilot. The performance mods that go along with the bigger tip tanks include a re-designed trim tab and the CG envelope has been expanded.
Interesting spy story, though. I would think that unless you had someone standing directly next to the tail, it'd be tough to get accurate numbers. Even then, you'd have to know your exact distance to the camera and the exact focal length of the lens. If it was a zoom, that'd be nearly impossible.