  Stabilization schemes in wall-bounded flows often invoke fluid transpiration
through porous boundaries. While these have been extensively validated for
external flows, their efficacy in channels, particularly from the standpoint of
non-modal perturbations, is yet to be demonstrated. Here, we show that
crossflow strengths previously considered ``ideal'' for optimizing stability in
channels in fact admit strong non-modal energy amplification. We begin by
supplementing existing modal calculations and then show via the resolvent that
extremely strong and potentially unfeasible crossflows are required to suppress
non-modal growth in linearly stable regimes. Investigation of unforced
algebraic growth paints a similar picture. Here, a component-wise budget
analysis reveals that energy redistribution through pressure-velocity
correlations plays an important role in driving energy growth/decay. The
superposition of a moving wall is also considered, and it is shown that while
energy amplification generally worsens, it can potentially be suppressed beyond
a regime shift in parameter space. However, these flows are marred by rapidly
declining mass transport, rendering their ultimate utility questionable. Our
results suggest that crossflow-based stabilization might not be useful in
internal flows.
