public class CustomGanttViewTimelineElementProvider : GanttViewTimelineElementProvider
{
    public CustomGanttViewTimelineElementProvider(GanttViewGraphicalViewElement owner) : base(owner)
    {

    }
    public override IVirtualizedElement<GanttViewTimelineDataItem> CreateElement(GanttViewTimelineDataItem data, object context)
    {
        GanttViewTimelineItemElement element = this.OnItemElementCreating(data);

        return new CustomGanttViewTimelineItemElement(data, Owner);
    }
}

public class CustomGanttViewTimelineItemElement : GanttViewTimelineItemElement
{
    public CustomGanttViewTimelineItemElement(GanttViewTimelineDataItem data, GanttViewGraphicalViewElement graphicalViewElement) : base(data, graphicalViewElement)
    {

    }
    public override GanttViewTimelineItemBottomStackElement CreateTimelineItemBottomStackElement()
    {
        return new CustomGanttViewTimelineItemBottomStackElement();
    }
}

public class CustomGanttViewTimelineItemBottomStackElement : GanttViewTimelineItemBottomStackElement
{
    public CustomGanttViewTimelineItemBottomStackElement() : base()
    {

    }
    protected override SizeF MeasureOverride(SizeF availableSize)
    {
        if (this.Children.Count == 0)
        {
            return availableSize;
        }
        return base.MeasureOverride(availableSize);
    }
    protected override SizeF ArrangeOverride(SizeF finalSize)
    {
        if (this.Children.Count == 0)
        {
            return finalSize;
        }
        return base.ArrangeOverride(finalSize);
    }
}

protected override void OnLoad(EventArgs e)
{
    base.OnLoad(e);
    this.radGanttView1.GanttViewElement.GraphicalViewElement.TimelineContainer.ElementProvider = new CustomGanttViewTimelineElementProvider(this.radGanttView1.GanttViewElement.GraphicalViewElement);
    this.radGanttView1.DataProvider = new GanttViewIntegrationProvider(this.radScheduler1);
}