how to deal with the interface mesh problem for modeling metallic-dielectric structures when using VSIE in the feko

I  model  metallic-dielectric antenna, as shown in figure 1,the structure is composed of a cubic medium and a dipole antenna on the top layer. How to make the  surface mesh of the dipole antenna  coincide with the top surface of the volume mesh of the cubic medium. I want to use VSIE to solve the model. SIE for  metallic part (surface mesh) and VIE for the dielectric part(volume mesh)
. The interface of two part are overlapped, i had used union and subtract, but the output impedance matrix  is not what i want.