I've moaned about this for years. People can build as big a spinner as they like, but you're not allowed to effectively defend against it. I think it's so the Event Organisers can put on a good show. "Come and see these robots get ripped limb from limb". All you'd have to do in reality is duct tape a bit of duvet cover or nylon rope to the front of your wedge and aim at a spinner. Rather than snag you need to bind the blade at the axle. They won't allow it because it's boring to watch.