That only makes sense because the lizard is about a foot long though, where-as your creature is at least eight foot long in regards to its body and the Mech is only twice the size of a human. The space on top of the Mech for it to sit on is four foot long at most, so there's four feet of the creature's body unaccounted for that almost has to be dangling down the back of the Mech for it to make sense that it was able to attack the lens. Unless it's carrying out some immensely confusing contortions you haven't mentioned, such as sitting in a spiral on top of the Mech or something.