Google CSE - Hide Refinements for google stored CSE

Question

I have three websites using Google CSE. On two of the sites, I want the search refinements tab to show up. On the third site, I want to hide the refinements tab.

The overall search results appear in an iframe, so I don't know how to effect the css in it.

I believe I am using the "Google Stored CSE" approach to displaying results, which is briefly explained here: http://www.google.com/cse/docs/cref.html

So how do I hide the refinements on my third site only? I can't target the CSS of the elements in the iframe to do a display:none;