  Stop contributions to radiative corrections to R_b and the top quark decay
are analysed over the relevant MSSM parameter space. One sees a 30 % increase
in the former along with a similar drop in the latter in going from the
higgsino dominated to the mixed region. Consequently one can get a viable SUSY
contribution to R_b within the constraint of the top quark data only in the
mixed region, corresponding to a photino dominated LSP. We discuss the
phenomenological implications of this model for top quark decay and direct stop
production, which can be tested with the Tevatron data.
