  The duality angles deformation developed by de Roo and Wagemans within the
context of N=4 gauged supergravity is used in order to study certain classes of
gaugings of N=8 supergravity, namely, those that are consistent when halving
the maximal D=4 theory. After reviewing the truncation process from N=8 to N=4
supergravity in terms of the embedding tensor formalism, the de Roo-Wagemans
phases method is implemented for solving the resulting constraints on the
gauging parameters by means of the Schon-Weidner ansatz. In contrast with the
twenty semisimple N=4 gaugings admitting more than a single SL(2) angle
deforming their decompositions reported in the literature, it is proven that
only three of them can be embedded back into the N=8 theory. The scalar
potential derived for only two of these gauge groups exhibits an extremum in
the origin of the scalar manifold. These extrema are not stable under
fluctuations of all the scalar fields.
