CST - How to define properly a lossy-metal

Hello CST users, 

I am wondering, how should a lossy metal be properly defined? Should it be a 3D solid with a specified thickness in the parameter list, or a 2D thin sheet where thickness is set in the material definition?

When defining a new Lossy-Metal, both options exist. However, when using CST’s tabulated Gold (Lossy) material, the thickness cannot be set under the "coating" tab because "Gold" does not appear in the material list.

To define a thin lossy-metal layer, must one create a new Lossy-Metal material, select "Gold (Lossy)" under the coating tab, and assign a thickness?

Or is it correct to define it as a 3D solid with a specified thickness and simply apply the Gold (Lossy) material?

Thank you 

Gal

CST Studio Suite