Mori55 said:If I hit them they would definitely move up and the prop.
I guess you meant to say, "If I hit them, they would definitely move up and hit the prop".
However, that is not the same as saying, "I did hit them and they definitely moved up and hit the prop"
So which is it? You think that they might do? Or you actually tried it and they did? Because I just tried again to get a guard to touch the prop and, whilst it does move upwards very, very slightly when I push up hard on it, it doesn't reach the prop. In fact, if it's properly clicked in place, it's easier to tilt it downwards slightly than upwards.
But it's up to each user, I'm not selling the idea. In my case, I use them when there's a need - e.g. when flying close to buildings, or if there are other persons around. But if there is no need I leave them off. So it works great for me. If I had to use the screws, there's no way I'd bother to use them at any time, which might invite an expensive disaster.