Hello he seaman,
Setting different Bars Width for two or more Series Mappings is not possible with RadChart for Silverlight. The width depends on the axis range, the number of major / minor ticks and the ticks distance. After all these factors are taken into account, the bar width percent reduces the bar size by a percentage of the determined size. Knowing this I hope you understand that it is not possible to set different Width for every SeriesMapping you have. We are sorry for the inconvenience.
Also have in mind that using ChartArea.ItemWidthPercent
property you can control all Bars width.
the Telerik team
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