Custom HtmlEditorConfig and TinyMCE multiple rendering

_config.php

<?php

//skipping other config...

HtmlEditorConfig::get('mini')->setOptions(array(
  'friendly_name' => 'Mini editor',
	'priority' => '10',
	'valid_elements' => "@[id|class|style|title],a[id|rel|rev|dir|tabindex|accesskey|type|name|href|target|title"
		. "|class],-strong/-b[class],-em/-i[class],-strike[class],-u[class],#p[id|dir|class|align|style],-ol[class],"
		. "-ul[class],-li[class],br,"
		. "-sub[class],-sup[class],"
		. "-span[class|align|style],"
		. "@[id,style,class]"
));
HtmlEditorConfig::get('mini')->setButtonsForLine(1, array('bold','italic','underline','strikethrough','separator','sslink', 'unlink','separator','justifyleft','justifycenter','justifyright','justifyfull','separator','bullist','numlist','separator','charmap','selectall','code','separator','undo','redo','pastetext'));
HtmlEditorConfig::get('mini')->setButtonsForLine(2, array());
HtmlEditorConfig::get('mini')->setButtonsForLine(3, array());
HtmlEditorConfig::get('mini')->disablePlugins('media','fullscreen','contextmenu','table','emotions','spellchecker');
HtmlEditorConfig::get('mini')->enablePlugins(array(
	'ssbuttons' => sprintf('../../../%s/tinymce_ssbuttons/editor_plugin_src.js', THIRDPARTY_DIR)
));

Presentation.php

<?php
class Presentation extends DataObject
{
  private static $db = array(
    'Title'      => 'Text',
    'Description' => 'HTMLText'
	);

	public function getCMSFields()
	{
    HtmlEditorConfig::set_active('mini');
    $description = HTMLEditorField::create('Description', 'Short description');

		$fields = new FieldList(
			new TabSet(
				'Root',
				new Tab(
					'Main',
					$description					
				)
			)
		);

		return $fields;
	}
}