I'm still interested in seeing these experiments. I know there would be a big difference between 3 and 4 fin rockets. There would be a difference between square fins and rounded fins. There may not be to much difference in just the shape though as long as the fins are all about the same size. They would all have to be launched the same day under same wind conditions. I would launch the fins like this: 1,2,3,4,5...etc. and not 1,1,1,2,2,2,3,3,3..etc. This way if there is weather change, the experiment will be more accurate.
The rocket matches the home décor and will be able to sit out without the wife suggesting it be put away. Smart move.