maximum number of mesh elements - HFSS

Hi all,
I am trying to simulate a big structure and, even if I have a lot of memory and RAM, I need to reduce the number of mesh elements to avoid any memory problem.
Does anyone know how to assign a minimum size of the mesh element in order to avoid the number of mesh elements becomes to big?
Any rule of thumb on how much I can increase the length of the element preserving the result?

Thanks.

you can set the maximum normal deviation angle (try 60degrees) under surface approximation of mesh operations.

You can set the size of the cells Max:Lambda/10,further question?