Changing space between header and body

I've just installed Atahualpa for the first time and I love it. After modifying it for a couple hours, I'm stumped when it comes to changing the space between the header and the elements below it.

Here's a sample image:
http://animatusstudio.com/test/image...equestion1.gif

The design I'm trying to achieve requires the sidebars and page boxes to touch each other, bringing the body up to meet the header.

Any ideas?