[kh99]

Try creating a new plugin using hook fetch_threadinfo_query and this code:

if (THIS_SCRIPT == 'showthread')
{
   $hook_query_fields .= ", userfield.fieldX ";
   $hook_query_joins .= " LEFT JOIN " . TABLE_PREFIX . "userfield AS userfield ON(thread.postuserid = userfield.userid) ";
}

and of course you'll want to change the X to the actual field id.