coax setup in hfss

halo i am trying to figure out how the do the set up in hfss of the structure in hfss.i able to do the coax setup in case of simple patch.now everytime i try to create a probe of pec for sustrate and air on analysis i get error message that probe and air intersect.if i try to create a probe for air and probe for substrate seprately again i get error message.can any please help me with this.

anothere thing how much can i keep the distance between the gnd and substrate basically air without degrading the coax feed performance