so I broke down and created my own custom code to add to the postbit_legacy template so it would display the gamertag.
with the below code it will show the gamertag name and a thumb of the avatar if you hoover on each it will show the actual image and if you click on the gt it will take you to the compose message screen on xbox.live.com
Code:
<!-- xbox live gt -->
<div>
<vb:if condition="$post['field9']"><fieldset><legend>XBox LIVE Gamercard</legend>
<a href="http://avatar.xboxlive.com/avatar/{vb:raw post.field9}/avatar-body.png" target="_blank" onmouseover="gXBL_show('nxeavatar','{vb:raw post.field9}');" onmouseout="return gXBL_hide();"><img border="0" width="20" height="20" src="http://avatar.xboxlive.com/avatar/{vb:raw post.field9}/avatarpic-s.png" style="border: 1px solid gold;" /></a>
<a href="https://live.xbox.com/en-US/Messages?gamertag={vb:raw post.field9}" target="_blank" onmouseover="gXBL_show('gamercard','{vb:raw post.field9}');" onmouseout="return gXBL_hide();">{vb:raw post.field9}</a></vb:if>
</fieldset>
</div>
<!-- endxbox live gt -->
i usually place it right below the post.posts portion on the template. but you may want to play around and use it where you want.
if you're using the eTiKeT™ 2011 Posbit_legacy - Postbit modification for the threads then use the code like this:
Code:
<!-- xbox live gt -->
<div class="etiket_postbit_alanI_userinfo_extra_yazIlarI">
<vb:if condition="$post['field9']"><fieldset><legend>XBox LIVE Gamercard</legend>
<a href="http://avatar.xboxlive.com/avatar/{vb:raw post.field9}/avatar-body.png" target="_blank" onmouseover="gXBL_show('nxeavatar','{vb:raw post.field9}');" onmouseout="return gXBL_hide();"><img border="0" width="20" height="20" src="http://avatar.xboxlive.com/avatar/{vb:raw post.field9}/avatarpic-s.png" style="border: 1px solid gold;" /></a>
<a href="https://live.xbox.com/en-US/Messages?gamertag={vb:raw post.field9}" target="_blank" onmouseover="gXBL_show('gamercard','{vb:raw post.field9}');" onmouseout="return gXBL_hide();">{vb:raw post.field9}</a></vb:if>
</fieldset>
</div>
<!-- endxbox live gt -->