I agree, the "body bucking" is interesting. My other snakes will crawl off or make an effort to stay in their cages when not interested in coming out.
Wallace bucks like a horse and if you are not used to it, like I wasn't I was expecting a bite to follow. Now I'm used to the behavior.
I may resort to a string type measurement soon. The Serpent Widget used to be the answer but I've had results differ greatly when using the same snake and I'm not sold on it just yet.
I think he may shed tonight.