I have a working application of labels to a point array - but the size of the text is not relative to the map scale. This decreases the readability of labels when panning and zooming.

To resolve~

How would one implement a text-size based (ex: 'textSize = 7' below in code) on MapUnits?

    field = str(csvGridFieldNames[index])
    csvGrid = ftools_utils.getMapLayerByName(unicode('mfLayer1_Grid'))#str(activeLayer)))
    textSize = 7
    valLabel = QgsPalLayerSettings()
    valLabel.readFromLayer(csvGrid)
    valLabel.enabled = True
    valLabel.fieldName = field
    valLabel.placement= QgsPalLayerSettings.OverPoint
    valLabel.setDataDefinedProperty(QgsPalLayerSettings.Size,True,True,'%f' %(textSize),'')
    valLabel.writeToLayer(csvGrid)
    iface.legendInterface().refreshLayerSymbology(csvGrid)
    iface.mapCanvas().refresh()

Ergo, I'm lead to believe changes are nessecary in this statement:

    valLabel.setDataDefinedProperty(QgsPalLayerSettings.Size,True,True,'%f' %(textSize),'')

This looks like the path, but continual attempts return syntax errors...

Referenced via: QgsPalLayerSettings Class Reference