[markbolyard]

There is no header height defined. It's simply determined by two items; the Logo, and the Ad. Notice, if you remove this section of code:

<table border="0" width="$stylevar[outertablewidth]" cellpadding="0" cellspacing="0" align="center">
<tr>

  <td align="right" width="325">
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;
<a href="$vboptions[homeurl]"><img src="$stylevar[imgdir_misc]/logo.gif" border="0" alt="" /></a></td>
  <td align="right" width="100%">
	<table border="0" cellpadding="0" cellspacing="0">
	 <tr>

	  <td style="background-color:#DDDDDD;" valign="middle" class="navigation">
<script type="text/javascript"><!--
google_ad_client = "pub-9556872839910172";
google_alternate_color = "DDDDDD";
google_ad_width = 468;
google_ad_height = 60;
google_ad_format = "468x60_as";
google_ad_type = "text";
//2007-06-08: vBulletin Styles
google_ad_channel = "5984012549";
google_color_border = "DDDDDD";
google_color_bg = "DDDDDD";
google_color_link = "FFFFFF";
google_color_text = "FFFFFF";
google_color_url = "000000";
//-->
</script>
<script type="text/javascript"
  src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script> &nbsp;

	  </td>
	  <td>&nbsp; &nbsp;</td>
	 </tr>
	</table>
  </td>
</tr>
</table>

from the header template, you have just a small space above the nav area (this is because there is a <br /> in there too. Remove that to reduce that size... Anyhow, if you reduce the logo, the ad size has to be reduced as well. Hope this helps.