Hi Piotr, like you already found out, you can use whenBuiltDo: But instead of using #hResizing: , which is not explicit in specs api you can call the method hShrinkWrap (look in AbstractMorphicAdapter, protocol 'protocol'). Here is a small example with centering a label: | ui layout | ui := DynamicComposableModel new. ui title: 'hello'. ui instantiateModels: #( label LabelModel check CheckBoxModel text TextInputFieldModel button ButtonModel ). ui label text:'Hello World'. ui label whenBuiltDo:[: widget |widget widget hShrinkWrap.]. layout := SpecLayout composed newRow: [ :r | r add: #label] height: 25; yourself. ui openWithSpecLayout: layout. the block arguemt for whenBuiltDo: is a WidgetBuilt announcement, that gives you access to the model and the widget (-adapter) that is used. nicolai