title: Highstock - custom tooltip data not being displayed for larger dataset
body: <p>I've got a highstock chart that displays properly for a dataset that is about 100 long.</p>
  
  <p>I add a custom data to the point so that the tooltip displays this value.</p>
  
  <pre><code>  for j in i.data        
      point = 
        x:(moment(j[0], "YYYY-MM-DD").unix()) * 1000
        y:parseFloat(j[2])
        z:parseFloat(j[1])
  </code></pre>
  
  <p>And the tooltip is displayed via</p>
  
  <pre><code>  tooltip:
      pointFormat: '&lt;span style="color:{series.color};"&gt;{series.name}&lt;/span&gt;: &lt;b&gt;{point.z}&lt;/b&gt;&lt;br/&gt;',
      valueDecimals: 2
  </code></pre>
  
  <p>Above works fine and displays the "point.z" fine. But when I request a larger dataset, this value disappears. I compared the chart object and indeed the point.z value is gone.</p>
  
  <p>I have read elsewhere that you have to set the "turboThreshold" so I set the values as</p>
  
  <pre><code>  plotOptions:
      series:
        turboThreshold:100000
      line:
        turboThreshold:100000
  </code></pre>
  
  <p>But the "point.z" is still not being displayed. Any ideas?</p>