flex 4: creating a group that slides off stage during fullsize mode

Question

I have no problems getting this to work in smaller sizes, but as soon as the application goes to full screen it throws off all of the layout. Any suggestions?

here's the effects (stageWidth is updated on resize and I've checked that it contains the correct value).

    <s:Bounce id="bounceEasing"/>
    <s:Parallel id="panelIn">
        <s:Animate duration="2000" easer="{bounceEasing}">
            <s:motionPaths>
                <s:SimpleMotionPath property="visible" valueFrom="false" valueTo="true"/>
                <s:SimpleMotionPath property="x" valueFrom="{stageWidth}" valueTo="0" />
                <s:SimpleMotionPath property="width" valueFrom="0" valueTo="{stageWidth}" />
            </s:motionPaths>
        </s:Animate>            
    </s:Parallel>
    <s:Parallel id="panelOut">          
        <s:Animate duration="2000" easer="{bounceEasing}">
            <s:motionPaths>
                <s:SimpleMotionPath property="x" valueFrom="0" valueTo="{stageWidth}"/>
                <s:SimpleMotionPath property="visible" valueFrom="true" valueTo="false"/>
                <s:SimpleMotionPath property="width" valueFrom="{stageWidth}" valueTo="0" />
            </s:motionPaths>
        </s:Animate>            
    </s:Parallel>   

Here's the panel I'm trying to slide in & out. The group that surrounds the label and button can't be sized by percentage.

<s:Group id="aboutPanel" height="100%" width="0" visible="true">
    <s:Rect height="100%" width="100%" alpha=".85" >
        <s:fill>
            <s:LinearGradient rotation="90">
                <s:GradientEntry color="0x333333" />
                <s:GradientEntry color="0x000000" />
            </s:LinearGradient>
        </s:fill>
    </s:Rect>
    <s:VGroup height="100%" width="100%" horizontalAlign="center" >
        <s:Group height="230" width="280" verticalCenter="0" horizontalCenter="0">
            <s:Label id="aboutTitle"  text="this is my title" 
                     color="#000000" fontWeight="bold"  
                     fontSize="24" left="0" right="0"
                     textAlign="center" verticalAlign="middle" fontFamily="Arial, Helvetica, _sans" />  
            <s:Button id="closeAbout" label="CLOSE" height="25" bottom="2" 
                      horizontalCenter="0"  width="62" 
                      click="closeAbout_clickHandler(event)"/>              
        </s:Group>          
    </s:VGroup>
</s:Group>