Make your own custom bushes for slimlines, I would think most people prefer to do those on a mandrel and turn both pieces at the same time.
Or adapt or adopt an existing mandrel to suit your own needs.
http://www.penturners.co.uk/showthread.php?t=712&highlight=idea+mandrel+saver
Or turn them directly in the tube, there are no rules and it ain't complicated init?