Reduce Width of Submenus

Greetings -

I've learned so much about menus, Wordrpress and Atahualpa in the last few days. But I'm still wondering:

Is there ANY WAY to reduce the width of sub-menus below 7em? That width, coupled with the border-lines I'd like to use, makes things run into each other in a messy way. I know how to enlarge my page menu items in a static way, but having them at 7em takes up too much of the page. I know I've been asking many questions, but have been trying to fill in answers as I go.

my site is here

Thanks!
Josh