Stage outline borders - plz help

I am trying to create outline borders for a shape on the stage and then transform the borders to outline the entire stage.

I got 2 movieclips on my stage :

• mask_mc - (width:500, height:66)
• bg - (width:500, height:250)
• stage size - (width:500, height:250)

import flash.display.MovieClip;
import flash.display.Shape;
import com.greensock.*;
import com.greensock.easing.*;
var tw = TweenLite;
var _border:Shape;
var bannerWidth_Exp = bg.width;
var bannerHeight_Exp = bg.height;
var bannerWidth = mask_mc.width 
var bannerHeight = mask_mc.height 
var startX = mask_mc.x 
var startY = mask_mc.y  
function DrawBorder():void
{
          _border = new Shape();
          _border.graphics.lineStyle(1.0, 0x000000, 1.0, false, LineScaleMode.NONE);
          _border.graphics.moveTo(startX, startY);
          _border.graphics.lineTo(startX+bannerWidth, startY);
          _border.graphics.lineTo(startX+bannerWidth, startY+bannerHeight);
          _border.graphics.lineTo(startX, startY+bannerHeight);
          _border.graphics.lineTo(startX, startY);
          addBorders();
}
function addBorders():void{
          addChild(_border);
          _border.width = bannerWidth
          _border.height = bannerHeight
          _border.x = startX
          _border.y = startY
          trace("height: " + _border.height)
          tw.to(mask_mc,1,{x:0,y:0,width:bannerWidth_Exp,height:bannerHeight_Exp, delay:0});
          tw.to(_border,1,{width:bannerWidth_Exp,height:bannerHeight_Exp+3.5, delay:0,onComplete:tracer});
}
function tracer():void{
          trace("width: " + _border.width)
          trace("height: " + _border.height)
          trace("x: " + _border.x)
          trace("y: " + _border.y)
}
DrawBorder();

I am not sure why this actually works, I had to add 3.5px to : tw.to(_border,1,{width:bannerWidth_Exp,height:bannerHeight_Exp+3.5, delay:0,onComplete:tracer});

As the lines never reach the bottom fully.

I am tyring to get this code to work across any size mask_mc/bg combination.

if I dont use LineScaleMode.NONE

Line cut of on the right, are more visible on the bottom etc

Any help is much appriciated.

Regards,

Pavel