Multilayer Reflectarray Antenna

Hi, I am trying to simulate one of Jose. Encinar's paper titled " Reflectarray element based on aperture-coupled patches with slots and lines of variable length ". The design consists of four layers. I am not able to get my simulated results matched with the paper results using CST. Can anyone help me how to design multilayer structure with proper conditions. Is there something special that we need to consider in case of multilayer structure?

Thanks!

Dr. Encinar's antenna structure is very complicated and I think he doesn't use the commercial software for the simulations. I dont have experience on multi-layer constructions. I think alignment is important?