The Club that I started out shooting matches at have the double stacked setup with sad berms behind them. They are made out of heavy angle iron and are very stable. I can't say that I ever knocked off any animals due to a rail hit. I prefer this set up since it gets more banks of animals in a smaller place and the sand berms give you an idea of where you hit if you miss. I have shot at some ranges with steel backing behind the stands and have seen the splatter knock animals off. Of course, this is just my preference.