Besides the thruster bells, what other mods did you do? I'm not very familiar with Endless Waltz designs, so I might have missed them. The neck looks a little too tall to me, but that might be the kit's shortcoming and not you. It could have used some shortening or bulking up of the neck area.
Other than that the finished work looks great. Nice subtle weathering and I dig the paint job. If I remember right, the Serpents had a tan - brown legs/arms and torso and a greenish gray chest and shoulders, but I like the white on olive drab a whole lot better. More contrast, which I'm all about. Good work.