With the legend position set to the top or bottom, the chart seems to be trying to center the legend horizontally according to the plot area. It clearly is not doing it correctly. It is more obvious when there is only one item in the legend.
I know that this can all be tweaked manually using positions and margins and so foth, but in our application we wish to only expose the legend position to the user.
Legend not being centered correctly
Legend.topPos = 0 fixes problem
I found that if I set the topPos to 0 that it centers correctly.