  A recently modified method to enable low-energy nuclear scattering results to
be extracted from the discrete energy levels of the target-projectile clusters
confined by harmonic potential traps is tested. We report encouraging results
for neutron--$\alpha$ and neutron--$^{24}\mathrm{O}$ elastic scattering from
analyzing the trapped levels computed using two different ab initio nuclear
structure methods. The $n$--$\alpha$ results have also been checked against a
direct ab initio reaction calculation. The $n$--$^{24}\mathrm{O}$ results
demonstrate the approach's applicability for a large range of systems provided
their spectra in traps can be computed by ab initio methods. A key ingredient
is a rigorous understanding of the errors in the calculated energy levels
caused by inevitable Hilbert-space truncations in the ab initio methods.
