We find that in addition to hollowing the spheres, it is also beneficial to deposit a thin ITO film,o n top of the gold substrate (the permittivity of ITO is modeled via an empirical Drude model with plasma frequency $\omega_p=1.46\times 10^{15}$ rad/s and decay rate $\gamma = 1.53\times 10^{14}$ rad/s). The ITO layer acts to decrease the equilibria separations and therefore increase the Casimir interactions between the spheres and the substrate. However, because the Casimir force between teflon/silicon and ITO is attractive/repulsive at small separations, respectively, increasing $H$ pushes the silicon-substrate’s unstable equilibrium to smaller separations while *introducing* a teflon-substrate unstable equilibrium that gets pushed to larger separations. In what follows, we find that $H$ from 14–30 nm is sufficient to obtain experimentally feasible suspensions, although here we only consider the case of $H=15$ nm. The effect of hollowing the spheres is shown in the top panel of [Fig. \[fig:fig6\]]{}: smaller $\alpha$ values push the stable/unstable bifurcation of teflon out to larger $R$. Hollowing the silicon sphere is not necessary because silicon has no unstable equilibrium (in this configuration it is repulsive down to zero separation). However, as shown in the bottom panel of [Fig. \[fig:fig6\]]{}, hollowing the silicon sphere 