menu background height

Hi, loving your theme, I am using it on a number of websites now. I am trying to modify the menu so that each menu item has a background colour. I have managed to get the following ” http://i.imgur.com/LZiq2BN.png ” with the code below. How do I change the height of the background colours to the following ” http://i.imgur.com/eOfVmgK.png ” and also position the menu so it sits in the centre vertically to the menu.

#header_main {
border-bottom: none;
background: #fff;
padding-bottom: 60px;}

.logo { height: 158%; }

#top .main_menu { padding-top: 20px; text-transform: uppercase;}
#top .main_menu .menu li { margin-right: 10px;}
#top .main_menu .menu li a { background-color: #95979c; color: white;}
#top .main_menu .menu li a:hover { background-color: #4b475e; color: white;}