CRUD Registration entities with Web services

First of all, many thanks to you guys for sharing and maintaining this module. On our project, it takes a core role.

We are currently setting up a Web service via Services → and to handle CRUD on the registration entities, we use Services Entity API → .

So far so good. But we ran into problems referring the rights management of the user_uid and author_uid fields of the object, which do have read only access. So we can retrieve, update and delete actual existing registration instances (created within drupal system), but are not able to create new registrations associated to the user via the App.

Is there any possibility, not to be forced to modify your module code, in order to create a fully filled and referenced registration instance? Or, if not, does it make sense (security issue) to modify permissions in code directly?
As the project ist already running, and we don't want to interfere with the current permission settings, we are curious about changing core code and asking therefore you for support.

Thank you very much for reading and for answering our support question.