charting.chartTitle is the key that you use to set the text value of the chart title, and since the key actually predates the Flash charting system, it's not the flash player drawing that little title at all, but rather the Javascript and HTML of the FlashChart module.
The good news is that you can control it with a little custom CSS. The class is "chartTitle", and you can see it sitting out there for yourself if you use a DOM inspector like Firefox's Firebug plugin.
So you can add this to your application.css file, or create a custom.css file to hold it.
.FlashChart .chartTitle {
font-size:15px;
}
BONUS: If you are used to the advanced XML and you happen to already be using Sideview Utils, then you can have much more direct control over all this. Specifically, you can also render your own text into a header without too much trouble. And if you want to define an on the fly convention like charting.chartTitle.fontSize, you can. See example below:
<module name="HTML">
<param name="html"><![CDATA[
<h2 style="font-size:$charting.chartTitle.fontSize$;">
$charting.chartTitle$
</h2>
]]></param>
</module>
