  We present here a relationship among massive self-dual models for spin-3
particles in $D=2+1$ via the master action procedure. Starting with a first
order model (in derivatives) $S_{SD(1)}$ we have constructed a master action
which interpolates among a sequence of four self-dual models $S_{SD(i)}$ where
$i=1,2,3,4$. By analyzing the particle content of 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 fourth order $K$-term in the spin-2
case and the analogous fourth order term in the spin-3 context.
