[F8] ¿Cómo puedo dejar de miniaturas de la superposición entre sí?

/**********import classes**********/
import mx.transitions.*;
import mx.transitions.easing.*;
/**********declare variables and instances**********/
var nextX = -440;
/**********create objects**********/
var xmlPhotos:XML = new XML();
var initThumb:Object = new Object();
/**********handle events**********/
xmlPhotos.onLoad = function() {
    for (var i:Number = 0; i<xmlPhotos.firstChild.childNodes.length; i++) {
        initThumb.photo = (xmlPhotos.firstChild.childNodes[i].attributes.photo);
        initThumb.desc = (xmlPhotos.firstChild.childNodes[i].childNodes[0].firstChild.nodeValue);
        makeAThumb(i);
        nextX += 100;
    }
    setInterval(_root,"scroller",50);
};
initThumb.onRollOver = function() {
    var moveX = this._x-10;
    thumbScaleX = new Tween(this, "_xscale", Bounce.easeOut, this._xscale, 120, .5, true);
    thumbPositionX = new Tween(this, "_x", Bounce.easeOut, this._x, moveX, .5, true);
    thumbScaleY = new Tween(this, "_yscale", Bounce.easeOut, this._yscale, 120, .5, true);
};

initThumb.onRollOut = function() {
    var moveX = this._x+10;
    thumbScaleX = new Tween(this, "_xscale", Bounce.easeOut, this._xscale, 100, .5, true);
    thumbPositionX = new Tween(this, "_x", Bounce.easeOut, this._x, moveX, .5, true);
    thumbScaleY = new Tween(this, "_yscale", Bounce.easeOut, this._yscale, 100, .5, true);
};
initThumb.onRelease = function() {
    txtTitle.text = this.photo;
    txtDesc.text = this.desc;
    mcLargePhoto.loadMovie("images/large/"+this.photo+".png");
};
/**********functions**********/
function makeAThumb(num) {
    var thumbName:String = "mcThumb"+num;
    panelBottom.mcScroller.attachMovie("thumb",thumbName,num,initThumb);
    panelBottom.mcScroller[thumbName].mcPhoto.loadMovie("images/thumbs/"+panelBottom.mcScroller[thumbName].photo+".png");
    panelBottom.mcScroller[thumbName]._x = nextX;
    panelBottom.mcScroller[thumbName]._y = 0;
    panelBottom.mcScroller[thumbName]._xscale = 100;
    panelBottom.mcScroller[thumbName]._yscale = 100;
}
function scroller() {
    //if (this._ymouse>mcScroller._y) {
    var scrollSpeed = (this._xmouse-Stage.width/2)/15;
    if (Math.abs(scrollSpeed)<1) {
        scrollSpeed = 0;
    }
    panelBottom.mcScroller._x -= scrollSpeed;
    if (panelBottom.mcScroller._x>0) {
        panelBottom.mcScroller._x = 0;
    } else if (panelBottom.mcScroller._x<Stage.width-panelBottom.mcScroller._width) {
        panelBottom.mcScroller._x = Stage.width-panelBottom.mcScroller._width;
    }
    updateAfterEvent();
}
/**********set properties**********/
xmlPhotos.ignoreWhite = true;
/**********run now**********/
xmlPhotos.load("photos.xml");
panelBottom.createEmptyMovieClip("mcScroller",this.getNextHighestDepth());
panelBottom.mcScroller._x = 0;
panelBottom.mcScroller._y = -78;