Inverted Axis Panning Direction with 2 Range Axes in JFreeChart?

Inverted Axis Panning Direction with 2 Range Axes in JFreeChart?

I have a chart with 2 range axes. I have the datasets mapped properly to
the two axes, but when I pan the chart, they move in opposite directions
(one goes up, one goes down)? Is there a way to invert the pan direction
while maintain the order of the axis labels? I want negative values on top
of both axes, and positive on the bottom; I just need the movements
synced.
It's not obvious to me if the pan direction is setable in any way
(although I could see this being desirable).
I asked this on the official JFreechart Forum, but haven't had any luck
with replies yet.