We present here a relationship between massive self-dual models for spin-3 particles in D = 2 + 1 via the master action procedure. Starting with a first-order model (in the derivatives) S S D(1) we have constructed a master action which interpolates between a sequence of four self-dual models S S D(i) where i = 1, 2, 3, 4. By analyzing the particle content of the mixing terms, we give additional arguments that explain why it is apparently impossible to jump from the fourth-order model to a higher-order model. We have also analyzed similarities and differences between the fourthorder K -term in the spin-2 case and the analogous fourthorder term in the spin-3 context.