Can I shut off the filter that is removing an iframe?

Thanks Alex!

The code worked great. As a work-around I was putting the iFrame inside of a plain old text widget. But now I can have the iFrame inside a hero image that is in a sequence.

I added a couple more tags to get the effect I was looking for:

/**
* Add iFrame to allowed wp_kses_post tags
*
* @param string $tags Allowed tags, attributes, and/or entities.
* @param string $context Context to judge allowed tags by. Allowed values are 'post',
*
* @return mixed
*/
function custom_wpkses_post_tags( $tags, $context ) {
	if ( 'post' === $context ) {
		$tags['iframe'] = array(
			'src'             => true,
			'height'          => true,
			'width'           => true,
			'frameborder'     => true,
			'allowfullscreen' => true,
			'style' => true,
			'marginwidth' => true,
			'marginheight' => true,
			'vspace' => true,
			'hspace' => true,
			'allowtransparency' => true,
			'scrolling' => true,
		);
	}
	return $tags;
}
add_filter( 'wp_kses_allowed_html', 'custom_wpkses_post_tags', 10, 2 );

Thanks again for your help. The SiteBuilder plug-in is great!