Is the radius of the feed wire (which is used to define a wire port) important in this model?

Modeling the Powerbus with Microstripes

The default wire radius was 1e-6 mm, which had a significant influence on the input impedance. Figure 1 shows the peculiar input impedance obtained using the default wire radius. The imaginary part rises on average as the frequency increases. The wire radius needs to be set to a realistic value. 0.5mm was used in this model.

Fig. 1. Input Impedance obtained with default feed-wire radius.