Okay, my site is down so I can't test this.
This code uses a combination of my rpg menu hack and the collapsable postbit, with a code fix from Oblivion.
I'm totally guessing here but PLEASE let me know if it works. Because if it does I'll likely be able to do my collapsable postbit without a code edit
So, just add this where you want it.
Code:
<!-- ##### START HACK - Gamertag Info ##### -->
<if condition="$post[field8]!=''">
<span class="smallfont"><b>Gamertag:</b> <div id="gamertagpostmenu_<if condition="THIS_SCRIPT == 'private'">99<else />$post[postcount]</if>">$post[username]<script type="text/javascript"> vbmenu_register("gamertagpostmenu_<if condition="THIS_SCRIPT == 'private'">99<else />$post[postcount]</if>", true); </script>
</div>
<div class="vbmenu_popup" id="gamertagpostmenu_<if condition="THIS_SCRIPT == 'private'">99<else />$post[postcount]</if>_menu" style="display:none">
<iframe src="$post[field8]" scrolling="no" frameBorder="0" height="140" width="204"></iframe>
</div>
<br />
</if>
<!-- ##### END HACK - Gamertag Info ##### -->
I suck at html so I'm really not sure how the iframe and div will interact.
Also, I'm guessing that field8 they put the full url in?