I bent or broke blades and had to replace a number of aluminum props until I went to stainless. I've been running stainless props now for better than 25 years, and I would never go back. All the guys I duck hunt or fish with run stainless props also, and none of us has ever torn up a lower unit because we hit something with it. When I'm duck hunting, I'm jumping logs and beaver dams, hitting the bottom in shallow water and hitting all kinds of logs, limbs, brush, etc., so I've been giving them a good test. I've never had any trouble other than the occasional burr which I could file off. I agree with the comment above that you're more likely to tear up a lower unit running a regular prop with a bent or broken blade.