the LineGapPlot with StepMode = STEP_START or STEP_END does not work as expected. It looks the upper line uses the specified step mode, while the lower line uses opposite setting (STEP_END if StepMode is STEP_START).
One can easily test it by adding the following lines to LineGap.cs/InitializeChart() method in MiscCharts demo.
// line gap plot thePlot1.StepMode = ChartObj.STEP_START; // multi line plot thePlot2.StepMode = ChartObj.STEP_START;