A hidden fuel line shut off with the main fuse pulled and parked in a manner that makes towing it out a hard task. Most thieves will try to drive it out and many will look for one trick like the main fuse but not many will take the time to look for two. If it was mine I would definitely look into buying an old box truck or container to park it in if it was going to be way out there with no one watching it. You know what they say out of site out of mind.