Having a look around the theme files i found two places:
style.css
.header-image .site-title a {
float: left;
min-height: 164px;
width: 100%;
}
functions.php
// Add support for custom header
add_theme_support( ‘genesis-custom-header’, array(
‘width’ => 360,
‘height’ => 164
) );
Can someone confirm that these are the ones that need to be changed? Thanks!