removing border of a panel in flex

Is there a way to remove the left+right+bottom border of a mx:Panel?

basically I want to have the right UI instead of the left one ( check the screenshot )

I know that the defa开发者_JAVA技巧ult spark Panel is able to do so, but I just need to use Flex 3.

Here is what I tried already :

• padding (seems only changing the children)
• borderStyle = none is removing the color of the header

Specify the following styles for your panel:

borderThicknessLeft: 0;
borderThicknessTop: 0;
borderThicknessBottom: 0;
borderThicknessRight: 0;

There's quite useful Flex Style Explorer when you stucked with styles.