Chris, Marc, thank you for your helpful insight.

Marc, your solution is the perfect one for me, as you suggest addWidget does the job:

Qt Code: 
  1. frmRealParts = new CRealPartsForm(this); // add form with Real parts
  2. ui->stackedWidget->addWidget( frmRealParts, "Realparts" );
  3. frmDistParts = new CDistPartsForm(this); // add form with Distributor parts
  4. ui->stackedWidget->addWidget( frmDistParts, "Distributor" );
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Apart from improved partitioning in the designer and code, this approach also has two other very real advantages for me:

1. I can add tabs and stacked widget pages on the fly as the user requires them;
2. If it turns out the UI is better served for some pages as a modal / modeless dialog, I can just call ->exec() or ->show() instead!

Thanks again!