  We lay out a novel formalism to connect the isospin-symmetry breaking
correction to the rates of superallowed nuclear beta decays, $\delta_\text{C}$,
to the isospin-breaking sensitive combinations of electroweak nuclear radii
that can be accessed experimentally. We individuate transitions in the
superallowed decay chart where a measurement of the neutron skin of a stable
daughter even at a moderate precision could already help discriminating between
models used to compute $\delta_\text{C}$. We review the existing experimental
situation and make connection to the existing and future experimental programs.
