  In supersymmetric models a large average stop mass $M_S$ is well known to
both boost the lightest Higgs boson mass $m_{h}$ and also make radiative
electroweak symmetry breaking unnaturally tuned. The case of `maximal mixing',
where the stop trilinear mixing term $A_t$ is set to give $A_t^2/M_S^2 = 6$,
allows the stops to be as light as possible for a given $m_h$. Here we make the
distinction between minimal $M_S$ and optimal naturalness, showing that the
latter occurs for less-than-maximal mixing. Lagrange constrained optimisation
reveals that the two coincide closely in the Minimal Supersymmetric Standard
Model (MSSM) -- optimally we have $5 < A_t^2/M_S^2 < 6$. We discuss why the two
are not generally expected to coincide beyond the MSSM, and that even within
the MSSM different models should not be compared based on the $M_S$ necessary
to achieve a given $m_{h}$. The splitting between the two stop-mass eigenvalues
$m_{\tilde{t}_2} - m_{\tilde{t}_1}$ is shown to be unconstrained by naturalness
considerations.
