Flash MX 2004.
stroke.density
Property; a string that specifies the density of a stippled line. This property is available only if the stroke.style property is set to stipple (see stroke.style). Acceptable values are "very dense", "dense", "sparse", and "very sparse".
The following example sets the density property to sparse for the stroke style of stipple:
var myStroke = fl.getDocumentDOM().getCustomStroke();
myStroke.style = "stipple";
myStroke.dotSpace= 3;
myStroke.variation = "random sizes";
myStroke.density = "sparse";
fl.getDocumentDOM().setCustomStroke(myStroke);