I made the following tweak to make it work in youtube-channel-gallery.php file:
Put an onclick event in the link of the thumbnail:
onclick="document.getElementById(\'mainPlayerTitle\').innerHTML=\''. $title .'\'"
And then you have right after you player:
$content .= '<div class="mainPlayerTitleDiv"><label id="mainPlayerTitle">' . $title . '</label></div>';
Just have in mind that if the plugin updates, changes would be lost.