What are the reasons for rockets with dual fins? I have been looking through historical books of rockets, and aside from rockets with a second set of forward fins, I see very few with an aft dual fin setup. Is there an aerodynamic benefit from a dual fin setup vs. a single fin setup of similar shape and proportion? Is it only with hobby rockets because it looks cool? Does the forward fin (of an aft dual fin rocket) 'change the rules' for the aft fin? Why?