The ChartsDevice library itself is not a candidate for AutoScaling as it is not a visible control but only returns a bitmap to be displayed in an Image control. I expect that a Chart designed for QVGA and then displayed in an Autoscaled Image control on VGA probably looks terrible - although I haven't tried that as I am busy on other AutoScale related stuff.
I know that ChartsDevice does not work totally well 100% on VGA but I do not intend to produce a VGA aware version as the library is stuffed full of pixel level magic numeric constants which would be a nightmare to track down and amend. However I do have (I think!) a solution to displaying them as well as possible in an AutoScaled application. It will depend upon the application knowing that it might be AutoScaled and drawing the chart appropriately but that won't be difficult to code (I hope). Look out for a new version of ControlsExDevice once the next version of Basic4ppc is released.