You may notice in the form where the Chi/Rho overlap, there is a certain viewing of the cross of Christ that may be captured. After all, the X of the Chi turned sideways, looks like a stylized cross or type of Celtic cross. But, the Chi/Rho is also meant to remind us that before the cross, Christ was existing… in eternity. And that after the cross, after the grave, there is resurrection and life. So the Rho follows the Chi.