Resizing PHP-Loaded Image in a MC

I have loaded an image dynamically from PHP into a MC. The movie clip is 80X60 but the jpegs are all different sizes (but in the same proportions). I know that the MC takes the size of the image when it is loaded, but how do I constrain or lock the dimensions of the MC and the jpeg at 80x60? It works if I use _yscale and _xscale but I want the exact dimensions 80X60. Shouldn’t _height and _width work?

Here is the code I’m working with now:

myData = new LoadVars();
myData.onLoad = function(success)

function setpic(pic)

maxwidth = 80;
maxheight = 60;

if (pics._width > maxwidth) {
delete _root.onEnterFrame; = maxwidth;
// Adjust height to new scale =;
// Now check if image is too tall
if (pics._height > maxheight) {
delete _root.onEnterFrame; = maxheight;
// Adjust width to new scale =;