Superfish full width in Drupal

Superfish full width in Drupal

Hello!
Is it possible superfish menu to be automatically resized to full width? I have 1000px width region with 5 menu items. I can manually set
.sf-menu.sf-style-default
width: 100%

and

.sf-menu.sf-style-default li,
.sf-menu.sf-style-default.sf-navbar
 width: 20%;

But it isn't nice because menu items has text with different length.