so I'm making a bottle rocket

[Zovistograt]

It's going to be Daft Punk-themed (named "The Veridis Quo" and the fuselage will have all the lyrics from all the songs with lyrics on Discovery in a spiral format), but that's not the point.  What I want to know is, should I add secondary, smaller fins on the top?  It's going to be very tall so I thought it would be good to stabilize the top using a second set of wings.  Should they be smaller or larger?  I think smaller would make more sense, because if they were Too Long it would probably topple over, but I'm not so good at Aerodynamics.