Hey, thanks for getting back to me!
The only other object besides those pictured is a vacuum box containing the model. A radiation boundary has been applied to the faces of this box. Two other boundaries have been applied, those being PerfE boundaries on each of the conductors.
Regarding the port, when you say it should be in the gap, that means on top of the substrate? If so, is the only relevant dimension the width (to ensure that it touches both conductors), or does the length (along x axis) also play a role?