Adding a new option to toggle display

I've tryied to add a new option in the toggle display fieldset in a Zen subtheme. With no success.

Maybe is an core issue, but anyway I should know if I can actually do it in the Zen's subtheme.

Firts: inspected the form array to see what would I put in the code and, wondered that the theme-settings.php should be the right place to make things. I successfully added a new option entry on the toggle display fieldset with the following:

  $form['theme_settings']['toggle_myzensubtheme_sample'] = array(
    '#type'          => 'checkbox',
    '#title'         => t('Myzensubtheme sample'),
    '#default_value' => theme_get_setting('toggle_myzensubtheme_sample'),
  );

Second: added a new info entry for the features:

features[] = myzensubtheme_sample

And finally, added the a wondered variable to be setted, following what I could see in the page.tpl.php:

<?php if ($myzensubtheme_sample): ?>
  /* Do the cool things to be controlled through apperance interface */
<?php endif; ?>

Not working. No idea what to do for the success.

Are I missing something? Or the features can't be controlled through custom theme (zen subtheme)? Should it be needed to create some kind of hook in other code's place?

Thanks in advance!