You'll never get it included on the FL ID, too big. Your best bet would be go with another quasi-lawful ID that allows the cargo size and just SRP for it. Used to fly with a Junker L'ane a lot, can't remember who had it though. Was a decent combo. And you haven't even considered the inrp consequences. The brigands get pretty defensive about the use of their ships by outsiders. It can be done, but best get permission or be prepared to fly with a helmet on.