I like this question.
I have been playing a little with it and it has me stumped.
in the javascript reference it states we should be able to set the Length, Angle, Origin etc of a gradient object.
a statement such as:
alert(pathItem.fillColor.origin);
works fine and displays the origin, this also works with length and Angle.
But when you try to set these values it does not work.
it says nothing about it being read only.
Does anyone have any light to shed on this???