  We discuss two different configurations of U_PMNS=U_l^dagger U_nu with
maximal mixings in both U_l and U_nu. The non-maximal mixing angles are assumed
to be small, which means that they can be expanded in. Since we are
particularly interested in the implications for CP violation, we fully take
into account complex phases. We demonstrate that one possibility leads to
intrinsically large theta_13 and strong deviations from maximal mixings. The
other possibility is generically close to tri-bimaximal mixing, and allows for
large CP violation. We demonstrate how the determination of the theta_23 octant
and the precision measurement of delta_CP could discriminate among different
qualitative sub-cases. In order to constrain the unphysical and observable
phases even further, we relate our configurations to complex mass matrix
textures. In particular, we focus on phase patterns which could be generated by
powers of a single complex quantity eta=theta_C exp(i Phi), which can be
motivated by Froggatt-Nielsen-like models. For example, it turns out that in
all of the discussed cases, one of the Majorana phases is proportional to Phi
to leading order. In the entire study, we encounter three different classes of
sum rules, which we systematically classify.
