Flash - Programmatically Draw A Scalable, Curved Comic-book Balloon Tail?

As a UI specialist, I am often asked to build tool-tip displays and other sorts of popups that display text. One of styles clients seem most keen on is text in a comic-book balloon. I would like to create this balloons programmatically (as opposed to embedding or linking to rendered graphics), because these balloons will have to change size at runtime, depending on how much text they have to hold.

Balloons are easy to draw for the most part: circles, rectangles or rounded-corner rectangles. The tough part, for me, is the tail (the little arrow-like part of the comic balloon that points towards the speaker). If you google comic balloon, you see that there are many varieties of tails. They ones clients request from me most often are curved. E.g...

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The tail will always be on the bottom of the balloon, and it will sometimes point left and sometimes point right. I have been trying to come up with tail-drawing algorithms for a while, but I'm not happy with the results. I'm basically stumbling around in the dark, changing variables, looking at the results, and using trial and error to try to move closer to the magic numbers that will work. "Work" just means a result that looks pleasing, which I realize is subjective. Most of my clients will be a happy with anything that looks reasonably good and professional.

I want this result to scale. And it would be great if it could work with as few inputs as possible, maybe just isFacingLeft, tailWidth and tailHeight (Which could maybe be a percentage of the whole balloon). Maybe an adjustable curveAmount.

If it matters, I'm using Flash/Actionscript, but any system that has some sort of turtle graphics engine should work pretty much the same way: I'm working with that standard flipped Cartesian grid (y increases downward), x and y coordinates, the ability to move a pen, draw lines and draw curves.One caveat: Flash only allows me to draw 3-point bezier curves -- start point, control point, end point.

Note: balloons won't have to scale after the are drawn.