I tried using [[module Search mini="true"]] but for some reason I can't seem to make it appear at the right size.
It works perfectly fine on my website (http://cyclods.wikidot.com/start), so I'm not sure why it's not working here.
Being able to use the search module will remove the need to edit the CSS every time a menu item is added/removed.
Size of the input field seems fixed to 30. I'll make a change request that the 'mini' form has a smaller field, maybe half that.