How to extend sf_event_mgt with own fields (additional changes after creation of own extension)

EventController.php

<?php
namespace YOURNAMESPACE\YourExtKey\Controller;

class EventController extends \DERHANSEN\SfEventMgt\Controller\EventController {

	/**
	 * Saves the registration
	 *
	 * @param $registration \YOURNAMESPACE\YourExtKey\Domain\Model\Registration
	 * @param $event \DERHANSEN\SfEventMgt\Domain\Model\Event
	 * @validate $registration \DERHANSEN\SfEventMgt\Validation\Validator\RegistrationValidator
	 * @return void
	 */
	public function saveRegistrationAction(\YOURNAMESPACE\YourExtKey\Domain\Model\Registration $registration, \DERHANSEN\SfEventMgt\Domain\Model\Event $event) {
		parent::saveRegistrationAction($registration, $event);
	}

}

ext_typoscript_setup.txt

config.tx_extbase {
    persistence {
        classes {
            DERHANSEN\SfEventMgt\Domain\Model\Registration {
                subclasses {
                    Tx_SfTapaEventfields_Registration = YOURNAMESPACE\YourExtKey\Domain\Model\Registration
                }
            }
            YOURNAMESPACE\YourExtKey\Domain\Model\Registration {
                mapping {
                    tableName = tx_sfeventmgt_domain_model_registration
                    recordType = Tx_YourExtKey_Registration
                }
            }
        }
    }
    objects {
        DERHANSEN\SfEventMgt\Controller\EventController.className = YOURNAMESPACE\YourExtKey\Controller\EventController
    }
}