Manipulators to stretch and move box

Hello everybody,

i have a little problem with adding manipulators to an visual via code, in my case a BoxVisual3D.

I define a box an two manipulators, one for moving, one for resizing:

var volumeBox = new BoxVisual3D();
volumeBox.Center = new Point3D(0, 0, 0);
volumeBox.Length = 0.3;
volumeBox.Width = 0.3;
volumeBox.Height = 0.3;
volumeBox.Material = MaterialHelper.CreateMaterial(Colors.SkyBlue, 0.3);

var xManipulator = new TranslateManipulator();
xManipulator.Color = Colors.Red;
xManipulator.Length = 0.4;
xManipulator.Diameter = 0.02;
xManipulator.Position = new Point3D(0, 0, 0);
xManipulator.Direction = new Vector3D(-1, 0, 0);
xManipulator.Offset = new Vector3D(-1, 0, 0);
xManipulator.Bind(volumeBox);

var xStretchManipulator = new TranslateManipulator();
xStretchManipulator.Color = Colors.SpringGreen;
xStretchManipulator.Length = 0.3;
xStretchManipulator.Diameter = 0.02;
xStretchManipulator.Position = new Point3D(0, 0, 0);
xStretchManipulator.Direction = new Vector3D(-1, 0, 0);
xStretchManipulator.Offset = new Vector3D(0, 0, 0);
//xStretchManipulator.Bind(volumeBox);

var binding = BindingOperations.SetBinding(
xStretchManipulator, TranslateManipulator.ValueProperty, new Binding("Length") { Source = volumeBox, Converter = new LinearConverter { M = 0.5 }});
binding.UpdateTarget();

//var targetBinding = BindingOperations.SetBinding(
//    xStretchManipulator, TranslateManipulator.TransformProperty, new Binding("Transform") { Source = volumeBox });
//targetBinding.UpdateTarget();
            
//var targetTransformBinding = BindingOperations.SetBinding(
//    xStretchManipulator, TranslateManipulator.TargetTransformProperty, new Binding("Transform") { Source = volumeBox });
//targetTransformBinding.UpdateTarget();

The code above works fine for resizing and moving the box, but the manipulator for resizing (xStretchManipulator) does not move with the box. When I add the transform-bindings to the xStretchManipulator, it moves with the box, but position is always in the center of the box and when you stretch to much, manipulator is inside the box.

Does anyone have an idea how to define and bind the manipulators, so that it works correctly?

Thanks a lot for any help or ideas!
christian