Set height of individual line in TextFlow?

Greetings,

I am having some trouble with a particular TextFlow I'm using which contains InlineGraphicElements.  Some of these sit below the line (by way of a negative baselineShift) and are thus colliding with the line below.

I would like to be able to increase the spacing between the graphic's line and the line below, but I can't find a way to do this.

I am able to get a reference to the InlineGraphicElement, which I'll call x

And a reference to the TextFlowLine and TextLine below this way:

var xPos:int = x.getAbsoluteStart();

var xLineFlowNum:int = this.textFlow.flowComposer.findLineIndexAtPosition(xPos);

var xTextFlowLine:TextFlowLine = this.textFlow.flowComposer.findLineAtPosition(xPos);

var xTextLine:TextLine = xTextFlowLine.getTextLine();

var nextTextFlowLine:TextFlowLine = this.textFlow.flowComposer.getLineAt(xlineNum + 1);

var nextTextLine:TextLine = xTextLine.nextLine;

So far so good, but I have no idea how I can increase the height of that next line.

TextFlowLine has a height property, but it's readonly.

and TextLine has a height property, but if I set it, it just rescales the text's height-- it doesn't increase the lineheight.

Does anyone know a way to individually control the line spacing in a TextFlow?