in my unsolicited opinion, that rocket was pretty close to flying. it did look a little under powered, but far worse was it's lack of balance. balance is harder to control w/ a single thruster. i don't know dick-lint about rockets, but my physics training suggests that single thruster rockets will be very difficult to keep balanced. many big rockets have dual thrusters often spread apart to create stability, right? i'm not saying you should complicate things w/ a dual thruster, i'm just saying the slightest moment about the center of gravity and your fubar'd. i would try your current design w/ slightly less baking soda and a more sophisticated balancing test.
-j
another option may be a long launch stabilizer bar. once beyond the bar, the rocket will have enough velocity for the aerodynamic stabilizers to take over. but that will prob have it's own issues--nevermind