CS3 : Sizing A Preloader To The Size Of The Movie Loading?

I have a preloader(as3) that is working great, I use FlashVars to pass it what movie it is loading, then it loads that movie, and shows it on the stage after loaded. I would like to make this a bit more dynamic. Right now I can use the same preloader for any movie so long as the movie and the preloader is the same size. I would like to pass the size of the movie im loading to the preloader with flashvars just like im passing it the file path for the movie itself. Here is how im passing the movie:

var swfLocation = this.loaderInfo.parameters.flashPath;
var myRequest:URLRequest = new URLRequest(swfLocation);

now i just access the variable wherever i want to say load the movie

I tried:

var swfHeight = this.loaderInfo.parameters.flashHeight;
var swfWidth = this.loaderInfo.parameters.flashWidth;
stage.stageHeight = swfHeight;
stage.stageWidth = swfWidth;

then in my flashvars i have a value of flashPath=<?=path?>&flashHeight=<?=height?>&flashW idth=<?=width?> (passing these to the embed and object using php btw)