adjusted so as to recover the correct hypercharges, where $Y/2 = T^{3}_{R} + Q_{X}$ with $T^3_{R}$ the third $SU(2)_{R}$ generator and $Q_{X}$ the $U(1)_{X}$ charge. As motivated above, we wish $Q_3$ to be part of a bi-doublet, and an economical choice is to embed it in a ${\bf5}_{2/3}$ of $SO(5)$ (the subscript refers to the $U(1)_X$ charge). As discussed in [@Carena:2006bn], it is preferable to place $t_R$ in a seperate ${\bf 5}_{2/3}$ to avoid large negative corrections to the $T$ parameter. $b_R$ is part of a ${\bf 10}_{2/3}$, allowing for the bottom Yukawa coupling, and the first and second generations are replicas of this structure in order to generate CKM mixing in a straight-forward way. Enhanced coupling to bottom quarks is also potentially a signal of RS attempts to explain the observed deviation in $A_{FB}^b$ [@Djouadi:2006rk].

The scan over parameters of [@Carena:2007ua] prefers that the quarks and leptons of the first two generations are localized close to the Planck boundary in order to suppress flavor changing neutral currents. The expanded custodial symmetry, combined with relatively light KK modes for the $Q_3$ custodial partners, is so efficient at suppressing contributions to the $T$ parameter, that it reduces some of the usual 