There is a really cool program for designing and simulating model rockets called OpenRocket. You can input the dimensions and specs of your rocket in great detail, then you can run simulations of it. Its pretty amazing.
Bix, you should consider inputing your rocket design and running some simulations. It might give you ideas for design features you'd like to try.
Note: Be careful when downloading this app. It goes to a page that asks you to put in a bunch of information, but if you read carefully, you don't have to enter anything at all and the download has already started.