[Ntrails]

At the risk of being dumb, wouldn't an easier solution be physical? ie have a usb stick with two actual "disks" and a an appropriately obscured physical switch to define what plugging it in actually does?

Again, this isn't going to beat someone who knows you've got something to hide, they can physically deconstruct/analyse the drive, but at least it's not going to be found by automatic scanning/software etc?