  We introduce a four-dimensional quantum model for describing the torsional
control of $\rm G_{16}$-type molecules in the electronic ground state, based on
the symmetry-adapted variational method. We define conditions for which
lower-dimensional models, commonly used to simulate the strong-field control of
molecular torsions, are reliable approximations to a four-dimensional
treatment. In particular, we study the role of different types of
rotational-torsional couplings---the field-free coupling and the field-induced
coupling---and show that the conclusions recently drawn on the role of
rotational-torsional couplings in the process of torsional alignment are not
correct. Furthermore, we demonstrate how important an adequate description of
the molecular polarizability is for reliably predicting the torsional
alignment.
