RadChart supports only a single PlotArea i.e. a set of X/Y axes with their gridlines, so it seems you have already found the best approach for your needs. Just for the sake of completeness, I'd like to mention, that you can add multiple series in the same chart, but that would require re-using the PlotArea, as shown in the images here
. If you need this, just add as many ChartSeries as you need to the RadChart.Series collection.
the Telerik team
Q2’11 SP1 of RadControls for WinForms is available for download (see what's new); also available is the Q3'11 Roadmap for Telerik Windows Forms controls.