I'll answer here as well so we can reference it later on.
You could add something like the line below to your definition.xml file:
<Initiate Name="Chart.Dimension.0.Sort.ByYValue.Use" value="1"/>
There is a qvprops.htm file that exposes all the different chart properties. I've searched and searched but it seems we have removed it from the SDK so I'll just upload it here instead with reservations that it might be outdated.
qvpp-docs.zip 9.6 K