  We perform exact coupled-channels calculations, taking into account properly
the effects of Coulomb coupling and the finite excitation energy of collective
excitations in the colliding nuclei, for three Fm formation reactions,
$^{37}$Cl + $^{209}$Bi, $^{45}$Sc + $^{197}$Au, and $^{59}$Co + $^{181}$Ta. For
the $^{37}$Cl + $^{209}$Bi and $^{45}$Sc + $^{197}$Au reactions, those
calculations well reproduce the experimental total fission cross sections, and
a part of the extra-push phenomena can be explained in terms of the Coulomb
excitations to multi-phonon states. On the other hand, for the heaviest system,
the deep-inelastic collisions become much more significant, and the fission
cross sections are strongly overestimated. We also discuss the surprisingly
large surface diffuseness parameters required to fit recent high-precision
fusion data for medium-heavy systems, in connection with the fusion supression
observed in massive systems.
