HFSS lumped port sheet size

In HFSS, does the size of the lumped port sheet affect the simulation in any way ? Does increase or decreasing the has any effect ?

Thanks !

It depends on your structure. You have to choose correct size for each structure saying microstrip, waveguide or coax cable.

How could I choose the lumped port size? Can you explain more please?
My structure in a fat dipole 1 mm above a mushroom-like EBG. (See the picture, I've selected the antenna.)