Overlapped bubbles in SChartScatterSeries does not show border



I have configured by SChartScatterSeries to display bubbles with a border. 

I did this by setting the innerColor and color, then setting the radius to innerRadius +1.  It works just fine, except when the bubbles overlap.  At the overlap point the borders of the bubbles do not set shown, they just blur into one big blobby thing.

I would like to display a border around all my bubbles, even when they overlap.  Is this possible?