I am far from an expert, and you have probably already considered this, and I am guessing that since no one else has said anything that I am probably wrong.
That said, with the open rocket design, won't the front king and crown behave like a tube fin at the very front of the rocket? I.e., if the rocket transiently deviates off flight path won't the aerodynamic forces of that "tube" up front tend to encourage even more deviation?
Again, probably ignorance on my part, but seems like an open rocket design, unless the engine(s) are mounted far forward, will have a considerable further forward center of pressure that would require either much more nose weight and/or much more posterior fin surface area than a rocket with a nose cone in order to be stable.:confused2: