right, but that little bit of extra cooling at idle won't give you much benefit with twin electric fans. if you look at a factory shroud, there is a large taper to it, so it draws the air into the fan. with the design you posted above you basically have a flat sheet pan with two holes cut into it. while driving that will restrict more air flow, as the air has to make to tight turn just past the core. like I said, the good versions of those shrouds that mount electric fans, have louvers or spring loaded doors that open at driving speeds.
