It looks like I was mistaken about setting the header so everything else scrolls. In ATO>Style Header Areas you can wrap the header code in a div with an id and then position it a fixed. Here is an example of the type of code.
Here is what could go in the Style Header Area box
HTML Code:
<div id="fixed-header">%logo %image %page-right</div>
And here is what you would put in ATO>Add HTML/CSS Inserts>CSS Inserts. You will probably have to tweak the CSS
HTML Code:
#fixed-header {
width: 1000px;
position: fixed;
}
td#right, td#left, td#middle {
padding-top: 300px !important;
}