Featured Image Size

Hello all,
I’m using the Twenty twelve theme for redesign.everythingturkeyinc.com and having a problem making my featured image the same width as the navigation bar above and the text below. When I checked in Firebug, there is some extra spacing at the side and bottom of the image that is preventing it from using the whole space as coded. I’ve changed the size of the image so there is definitely enough image its just the margin on the featured image is messed up. Is there something in my code I can change to make this fit correctly in the space provided. Your help is truly appreciated. (I’ve made a copy of my theme in child theme)