How difficult is it to add a chart type? I'm interested in having a ComboChart option. Not being a module developer, the best I can do is to try to reverse-engineer the module code to see how to do it. I've scanned all of the module files and it looks like the only place you reference the Google Visualization API is in the module file. Could it be as simple as adding 'ComboChart' => t('Combo chart') to the function views_dataviz_types() array?