taking care of transforms with GetContourSegments and multiple models?

I'm trying to us GetContourSegments as shown in the Contour example but it doesn't seem to apply post transform. I've examined the code and it appears Visual3DHelper.Traverse<GeometryModel3D>(model1, this.AddContours); should take care of transforms?

I put out the example below and it gives the contours for the original sphere and not the end resulting scaled sphere.

Also is there a way to compute contours of a model group or is the only way computing contours of each object then joining them together?

Thanks.

Code:

        //add a sphere to the model
        MeshBuilder myMeshBuilder = new MeshBuilder();
        myMeshBuilder.AddSphere(new Point3D(0, 0, 0), 2);

        GeometryModel3D mySphere = new GeometryModel3D { Geometry = myMeshBuilder.ToMesh(true), Material = MaterialHelper.CreateMaterial(Colors.Pink), BackMaterial = MaterialHelper.CreateMaterial(Colors.Blue) };

        ScaleTransform3D scaletrans = new ScaleTransform3D(2, 2, 2);
        mySphere.Transform = scaletrans;

        ModelVisual3D myMod3d = new ModelVisual3D();
        myMod3d.Content = mySphere;

        view1.Children.Add(myMod3d);
        AddContours(myMod3d, 20, 20, 20);

//end result is the contoured original sphere and not the scaled up version

I would like to keep the GetContourSegments function as it is - working on a single MeshGeometry3D and not transforming the positions.
To support the transforms I think you should inverse(?) transform the position and normal of the contour plane! I think this is the best choice for performance...