I actually designed the legs to look like an offroad suspension. Since the Aliens can jump really far and are biomechanical I made the legs look like shocks and springs. Plus I changed the feet to be thickly padded so an animal that probably weights 500 or 600lbs could jump 20ft and land.
Everything was done with a purpose. I changed the tail from just two thick cables side by side like the movie to two cables that start in line with the body and then transition to the side by side cables of the movie. That way the tail is more compatible with the anatomy of a biped..