Extending Post Field Class (RWMB_Post_Field)

I'm attempting to create a new field by extending the RMWB_Post_Field with no luck so far.

Something like the code below works other than the actual Ajax request to load the posts. When it runs the AJAX request, it doesn't include any actions, so it results in a 400 error.

<?php
class RWMB_Proper_Link_Field extends RWMB_Post_Field {

    public static function add_actions() {
        return parent::add_actions();
    }

    static function html( $meta, $field ){
        return parent::html( $meta, $field );
    }
}

I've tried going through the docs, the parent class, and looking for examples online and just can't seem to figure out what the missing piece is here. Has anyone else run into this issue and knows the right way to approach extending the class?