  We assess the extent to which the flux-limited PSCz redshift sample is
capable of accounting for the major share of mass concentrations inducing the
external tidal forces affecting the peculiar velocities within the Local
Supercluster (LS). The investigation is based upon a comparison of the ``true''
velocities in 2 large N-body simulations and their reconstruction from
``observation-mimicking'' mock catalogues. The mildly nonlinear ``mock'' LS and
PSCz velocities are analyzed by means of the Least Action Principle technique
in its highly optimized implementation of Nusser & Branchini's Fast Action
Method (FAM). For both model N-body Universes, we conclude that the dipolar and
quadrupolar force field implied by the PSCz galaxy distribution would indeed be
sufficiently representing the full external tidal force field.
