As the transform is called RenderTransform, it affects only the rendering, but not the layout. To make a transformation that affects the layout as well you might use the LayoutTransformControl in the Telerik.Windows.Controls.Primitives namespace of the Telerik.Windows.Controls assembly. It applies render transform, but affects the layout as well.
Nevertheless I would recommend you just to make the user control bigger instead of transforming it, because transformations might make the content blurry.
Hope this information is helpful.
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