Average line in area graph

I want to show an area graph with an average line trough it. This is the search I'm using:

eventtype=windows_performance object=Process | timechart span=5m count as Alerts | appendcols [search eventtype=windows_performance object=Process | stats count as average | eval average=average/48] | eventstats first(average) as test | fields - average

What is does it create a timechart for the last 4 hours, then I search for the total number and divide it to match the timechart span (4hours = 240minutes, 240m/5m = 48)

This graph is almost showing what I want, but for the second series I want a line, not area.

Any ideas on how to to achieve this?

I have tried this sollution, but it shows colums for all series. Even a direct copy of the answer shows colums for every series. I'm using 6.0, could this be for an older version of Splunk? http://answers.splunk.com/answers/89399/add-a-line-overlay-to-a-column-chart

Here is the current XML for it:

<dashboard>
  <label>testtest</label>
  <description/>
  <label>sample overlay simple xml</label>
  <row>
    <chart>
      <title>testgraph</title>
      <searchString>eventtype=windows_performance object=Process | timechart span=5m count as Alerts | appendcols [search eventtype=windows_performance object=Process  | stats count as average | eval average=average/48] | eventstats first(average) as test | fields - average</searchString>
      <earliestTime>-4h@m</earliestTime>
      <latestTime>now</latestTime>
      <option name="charting.chart">area</option>
      <option name="charting.chart.nullValueMode">gaps</option>
      <option name="charting.chart.sliceCollapsingThreshold">0.01</option>
      <option name="charting.chart.stackMode">default</option>
      <option name="charting.chart.style">shiny</option>
      <option name="charting.drilldown">all</option>
      <option name="charting.layout.splitSeries">0</option>
      <option name="charting.legend.labelStyle.overflowMode">ellipsisMiddle</option>
      <option name="charting.legend.placement">right</option>
    </chart>
  </row>
</dashboard>