Away3D (4.x Broomstick) - How do I set the alpha of a material loaded with a 3DS file?

I have loaded a model using the 3DS parser that is already linked to a material and loads fine. I would like to make this model semi-transparent part of the time but not all of the time. I would like to just set alpha = .5 but when I target the materal that is not an option.

Here is the code and using:

        var slingPar:Max3DSParser = new Max3DSParser();
        var slingLoader:Loader3D = new Loader3D();
        sling = new ObjectContainer3D();
        slingLoader.addEventListener(LoaderEvent.RESOURCE_COMPLETE, function(e:LoaderEvent):void
        {
            var mesh:Mesh = Mesh(sling.getChildAt(0));
            mesh.material.lights = [light1, light2, light3];
            mesh.rotationY = 180;

        });
        slingLoader.load(new URLRequest("assets/game/slingCup.3DS"),slingPar);
        sling = slingLoader;

I tried

mesh.material.alpha = .5

But had no luck. Any Ideas?

I figured it out. I targeted the BitmapMaterial of the loaded mesh and modified from there.

slingLoader.addEventListener(LoaderEvent.RESOURCE_COMPLETE, function(e:LoaderEvent):void
        {
            var mesh:Mesh = Mesh(sling.getChildAt(0));
            var map:BitmapMaterial = mesh.material as BitmapMaterial;
            map.ambient = .5;
            map.specular = .5;
            map.alpha = .8;
            map.lights = [light1, light2, light3];
            map.repeat = true;
            map.smooth = true;
            map.bothSides = false;

        });