As of current rules a crew can ONLY be 7 people, how you make up the seven and the ranks they are is up to you. Crews cannot have anymore than 7, this includes what is known as hang around's. If you are looking to have hang around's they must be included in the 7 person limit. For more information on crews I would recommend joining the BBRP Crews discord and reading through the rules channel (including the document shared) thoroughly. And then applying in the welcome channel. Please note, that a crew that operates with more than 7 members will face punishment which may include permanent disbanding.
Good luck with your application if you choose to apply after going through the rules etc.