  We demonstrate in a proof-of-concept numerical hydrodynamics calculation that
the narrow radial filamentary structures seen in Pa 30 could be generated
through highly efficient cooling (e.g. via line emission) in the ejecta.
Efficient cooling in the ejecta causes a drop of pressure support in
Rayleigh-Taylor fingers, leading them to be compressed, and suppressing the
growth of Kelvin-Helmholtz instability. Following this result, we make three
predictions that could determine whether this is the mechanism responsible for
shaping Pa 30: First, we predict very strong emission lines, strong enough to
cool a significant fraction of the shock energy in an expansion time. Secondly,
we predict that the forward shock should be highly corrugated on small scales,
with the shock front closely following the structure of the filaments. Third,
we predict that these filaments should be nearly ballistic, with velocities
around 90% of the free-expansion velocity ($v \approx 0.9 ~r/t$). These
predictions should be falsifiable in follow-up observations of this remnant.
