There were at least 3 different size Estes flying R2-D2 models.
mini motor powered, smaller than:
std motor powered, but not quite as big as:
Big "oatmeal box" sized model for C6-3 motors.
Again, this is another of the long list of "short & fat" rockets that folks are drawn to like insects to a bug-zapper. Shot and fat rockets need nose weight and if you screw up the nose weight (i.e. if it is installed off center) it will make the rocket go unstable.
It helps somewhat that the fins extend below the fat body, but they certainly are not optimum fins (i.e. they stick out to the sides mostly and they are heavy soi they move the c.g. aft).