  Using a fermiology approach to the computation of the magnetic susceptibility
measured by neutron scattering in hole-doped high-Tc superconductors, we
estimate the effects on the incommensurate peaks caused by higher d-wave
harmonics of the superconducting order parameter induced by underdoping. The
input parameters for the Fermi surface and d-wave gap are taken directly from
angle resolved photoemission (ARPES) experiments on Bi{2}Sr{2}CaCu{2}O{8+x}
(Bi2212). We find that higher d-wave harmonics lower the momentum dependent
spin gap at the incommensurate peaks as measured by the lowest spectral edge of
the imaginary part in the frequency dependence of the magnetic susceptibility
of Bi2212. This effect is robust whenever the fermiology approach captures the
physics of high-Tc superconductors. At energies above the resonance we observe
diagonal incommensurate peaks. We show that the crossover from parallel
incommensuration below the resonance energy to diagonal incommensuration above
it is connected to the values and the degeneracies of the minima of the
2-particle energy continuum.
