Flex :: Horizontal Scrollbars - Dropdown Wider Than Anchor

I am using spark DropDownLists and I don't want to see any horizontal scrollbars in the dropdown. I'm OK with the dropdown being wider than the anchor, so I have a custom skin that sets popUpWidthMatchesAnchorWidth to false. But I don't want the dropdown to ever be smaller than the anchor. I came up with a solution that sometimes works, but there is something wrong with it. My DropDownList skin is as follows:

<?xml version="1.0" encoding="utf-8"?>
<s:SparkSkin xmlns:fx="[URL]" xmlns:s="library://ns.adobe.com/flex/spark"
xmlns:fb="[URL]" alpha.disabled=".5" minHeight="25">
<fx:Metadata>
[Code] .....

This works as expected when the contents of the dropdown are either wider than the anchor or smaller than about 100px, but if I explicitly set the width in the instance of the DropDownList to be something like 200px and the contents of the dropdown are around 150px wide, the dropdown is smaller than the anchor. Basically, it looks like openButton.getExplicitOrMeasuredWidth() returns about 100, regardless of what I set the DropDownList's width to be. How can I change this so that I can have multiple DropDownLists with different widths, but always making sure that the dropdown's width is either greater than or equal to the anchor's width?