As you and server density mention, this is a limitation of that chart and it isn't currently possible to detatch the axis and move it independantly of the chart. You might be able to gain a similar effect but it will probably take a little bit of improvisation on your behalf. For example, you could try shifting the tick mark positions, hiding the axis line, and drawing your own axis line. Or rendering a second chart that is synchronised via the scrolling delegate methods, and hiding the original chart's axes.
We've already got a task in our backlog to implement detatchable axes, but unfortunately it isn't a very popular feature so isn't very high on our development list at the moment. If you have any trouble finding an appropriate solution we'll try to give you advice where we can.