Mine are aluminum, I have dropped them on rocks like the situation you discribed earlier. They survived it.

I think if you were to break something in that case, or damage the rock rail, the maker would probably warranty it as its the soul purpose of the mod.

You will want something "boatsided" to protect your frame rails. If you drop the jeep on a rock, 1 of 2 things will happen, you will slide off outside, putting your door in danger, or slide off inside, where the rock ends up under your truck.