The potential energy surfaces of both components of the X²Π electronic ground state of the double Renner-Teller SiCN/SiNC system are calculated at RCCSD(T)-F12 level of theory. The SiNC minimum is found to lie at 628 cm^-1 above the SiCN one. The isomerization transition state is found at 7583 cm^-1 on the ²A' surface and at 7936 cm^-1 on the ²A'' surface. The cyclic local minimum on surface ²A' is also reproduced by our potential energy surface and is located at 3901 cm^-1. The calculated potentials are used to simulate ro-vibrational spectroscopy employing the recently developed EVEREST variational code. It is shown that Renner-Teller interaction (ε =0.3043 for SiCN and ε =0.3874 for SiNC) and spin-orbit coupling are both very important for a correct description of the spectroscopy of this system. Comparison with available experimental measurement is reported.