Set iconid when creating custom thread

[Ducks]

I'm using this to create threads from my own files:

// Backend files
    require_once('./global.php');
    require_once('./includes/class_dm.php');
    require_once('./includes/class_dm_threadpost.php');

// Setup Variables
    $forumid = 23; // The forum id that you want the thread posted in
    $postuserid = 1328; // The Userid of the poster
    $postusername = "Justin"; // The username of the poster
    $title = "This just in: " . $username . " joins our Forums..."; // The thread title

// Don't change below this line

// Start thread create
    $threaddm = new vB_DataManager_Thread_FirstPost($vbulletin, ERRTYPE_STANDARD);

    $username = htmlspecialchars_uni($username); 
    $allowsmilie = '1';
    $visible = '1';
    eval('$pagetext .= "' . fetch_template('welcome_thread') . '";'); 

// Insert thread
    $threaddm->do_set('forumid', $forumid);
    $threaddm->do_set('postuserid', $postuserid);
    $threaddm->do_set('userid', $postuserid);
    $threaddm->do_set('username', $postusername);
    $threaddm->do_set('pagetext', $pagetext);
    $threaddm->do_set('title', $title);
    $threaddm->do_set('allowsmilie', $allowsmilie);
    $threaddm->do_set('visible', $visible);
    $tid = $threaddm->save();

// Update last post stuff on forumdisplay
    require_once('./includes/functions_databuild.php'); 
    build_forum_counters($forumid);

But I've trouble adding an 'icon id', I've tried to add

$threaddm->do_set('iconid', '10');

And

$threaddm->do_set('iconid', 10);

But none of them work. Any ideas?