22 6 Recent analysis of LFV in 4D supersymmetric models with an A 4 symmetry can be found in [25]. • Electroweak precision tests . We have required the gauge couplings of the SM charged leptons to be in agreement with the SM prediction within 2 per mille accu- racy [29], both for neutral Z ¯ l$_{α}$l$_{α}$ and charged W ¯ l$_{α}$ν$_{α}$ currents. This is typically the present limit on the mixing of the electroweak gauge bosons with new resonances [45], models with warped extra dimensions [42]. The reason our model works so well regarding LFV is a combination of two types of flavor protection. The first one is the protection provided by the A$_{4}$ symmetry, which in simpler models with warped extra dimensions is enough to ensure agreement with experimental data [29]. In our case, due to the richer structure imposed by GHU models, this protection is not enough. This is where the second layer of flavor protection enters. Our model naturally falls in the optimal configuration discussed in [34]. The custodial symmetry, together with a LR symmetry originally proposed to protect the Z ¯ b$_{L}$b$_{L}$ coupling [9], and the splitting of the SM fields in two separate sectors ( ζ$_{1}$$_{,}$$_{2}$ and ζ$_{3}$$_{,α}$ in our case) reduce LFV in our model to values compatible with current data, despite the low scale of new physics. 6 We must require for the model to be realistic that it satisfies all experimental constraints. We can classify them in four types: those from EWPT, which we will estimate requiring small deviations from the SM tree-level couplings; limits on LFV processes which can proceed at tree-level; bounds on LFV processes which are banished to higher orders; and contraints from neutrino oscillations. The first three types of restrictions are mainly related to the heavy spectrum, whereas the latter one depends more directly on the discrete flavor symmetry breaking. Thus, although it involves less precisely determined parameters, it does restrict the model. The following phenomenological analysis must be understood as an existence proof. A refined analysis, which is outside the scope of this paper, should consistently include all contributions to a given order. We have done this for tree-level processes, but not for one-loop contributions which have been only estimated with the typically larger amplitude baring, for instance, possible cancellations. On the other hand, we have not considered one- loop corrections to Z ¯ eµ [43]. A detailed study of this type of constraints will be presented elsewhere, for they require a precise enough (numerical) treatment of fermion mixing to recover the proper behaviour of the different contributions, and then of decoupling [44]. The restrictions we explicitly consider are: