Hi Hans,
You can use panel side guidelines for this purpose - check out the following example:
All Examples \ Layout \ Aligning Chart Areas
The code of interest is:
// add a guide line on the left
NSideGuideline guideLine = new NSideGuideline(PanelSide.Left);
guideLine.Targets.Add(m_ChartStockValues);
guideLine.Targets.Add(m_ChartStockVolumes);
nChartControl1.document.RootPanel.Guidelines.Add(guideLine);
This will align the two charts on their left plot bounds.
Hope this helps - let us know if you meet any problems.