  In a previous letter (Phys. Rev. Lett. 96, 072502 (2006)), the multi-channel
algebraic scattering (MCAS) technique was used to calculate spectral properties
for proton-unstable $^{15}$F and its mirror, $^{15}$C. MCAS achieved a close
match to the then-new data for $p+^{14}$O elastic scattering and predicted
several unusually narrow resonances at higher energies.
  Subsequently, such narrow resonance states were found. New cross section data
has been published characterising the shape of the $J^\pi =\frac{1}{2}^-$
resonance. Herein we update that first MCAS analysis and its predictions. We
also study the spectra of the set of mass-15 isobars, ${}^{15}$C, ${}^{15}$N,
${}^{15}$O, and ${}^{15}$F, using the MCAS method and seeking a consistent
Hamiltonian for clusterisation with a neutron and a proton, separately, coupled
to core nuclei ${}^{14}$C and ${}^{14}$O.
