Here is the code from the EditHtml.ascx file...
<table cellspacing="2" cellpadding="2" summary="Edit HTML Design Table" border="0">
    <tr valign="top">
        <td colspan="2"><dnn:texteditor id="teContent" runat="server" height="400" width="600"></dnn:texteditor></td>
    </tr>
    <tr height="10"><td></td></tr>
    <tr>
        <td class="SubHead"><dnn:label id="plDesktopSummary" runat="server" controlname="txtDesktopSummary" suffix=":"></dnn:label></td>
    </tr>
    <tr>
        <td><asp:textbox id="txtDesktopSummary" runat="server" textmode="multiline" rows="10" width="600px" columns="75" cssclass="NormalTextBox"></asp:textbox></td>
    </tr>
</table>

You would think that would make the editor 600px wide. It does with FTB, but has no impact on CE.

Any other ideas?