In Momentum 2003C a facility exists to create thick metal structures. When I alter the thickness of the metal structure in the substrate definition I find that it doesn't alter the Z0 of the transmission line when in reality it should. I am measuring the Z0 using the mag(Z0) dataset from the data display window. The values of the S parameters are affected by varying the metal thickness. What is going wrong? Am I trying to measure the Z0 of a transmission line incorrectly? If so then what is the correct technique to determine the Z0 of a transmission line formed from thick metal?