I'm using FusionWidgets 3.x (purchased) and Flex 4.5.1... instantiating an instance of the Gantt Chart as:
chart = new FusionWidgets();
chart.FCChartType = "Gantt";
chart.percentWidth = 100;
chart.percentHeight = 100;
addElement( chart as IVisualElement );
The XML served up includes these two options:
ganttPaneDuration='2'
ganttPaneDurationUnit='d'
When the dataset is limited to 2 days or less - no problem. When the dataset spans 3 or more days - the scrollpane appears above the chart (effectively blocking it) and it looks like masking is broken. Here are two screenshots to help illustrate the problem.