Using Custom Attributes from rwmb_before_save_post action

OK, I give up. I need a point in the right direction here.

First: I very much love this plugin and all the extentinos. Every project I get to use this, I get a little more impressed. Well done! Now, on to my Issue...

I am attempting to use a custom attribute to control how exactly the meta data is saved. Specifically, I assign a attribute called mod_lock that I want to use from within the rwmb_before_save_post action. To make this work I need both the post_id and the $field array.

Custom Attribute is defined like-a-so:

'fields' => array(
               array(
                   'name'  => __('Favorite Monkey', 'monkey-monk'),
                   'id'    => 'fav_monkey',
                   'type'  => 'text',
                    'attributes' => array(
                        'mod_lock'  => true,
                    ),
               ),
            ),

Ultimately I would like to handle the savinging of the metadata something like:

function monkey_mod_save( $new, $old, $post_id, $field ) {
	$pre = '';
	if(!empty($field['attributes']['mod_lock'])){
		$pre = 'pending_';
	}

	if($new !== $old){
		$storage->update( $post_id, $pre.$field['id'], $new);
	}

	if( empty($new) ){
		$storage->delete( $post_id, $pre.$field['id'] );
	}
}

But this is the 'save' function... so I focused on the pre_save action, however all I have access to there is the $post_id and of course the $_POST data... but none of the delicious $field attributes.

I need your help, Obi-Anh!