I wouldn't be leaving a tail pack on the bike when it's unattended......also, you won't get a lid in a 30l Tailpack. .....or, at least, in a Kreiga Tailpack. A decent top box with a baseplate will be transferable between bikes.....just need a rack or adapter kit when you change bikes. One of my colleagues rides an FZ1 and when he goes off touring with his mates he has a secondhand pillion seat pad that he's screwed a topbox mounting plate to.....so he just fits that to the bike and puts the topbox on it and away he goes.....but when he's riding locally he just refits the standard pillion seat pad......