Different Widths?

To be able to style the menu items individually, you can make use of the WF parameter &rowIdPrefix .
If you f.e. add &rowIdPrefix=`item` to your WF call, the WF output might be like this:

<ul>
<li id="item4" class="first"><a href="index.php?id=4" title="Page A" >Page A</a></li>
<li id="item5"><a href="index.php?id=5" title="Page B" >Page B</a></li>
<li id="item8"><a href="index.php?id=8" title="Page C" >Page C</a></li>
<li id="item11" class="last"><a href="index.php?id=11" title="Page D" >Page D</a></li>
</ul>

That is, each row of the menu will get an own id which is composed by that rowIdPrefix and the ID of the document referred in this row (as you can see from the links).

li#item5 {
    width: 8em;
}