QMainWindow as child of QWinWidget

Hey peeps,

Has anyone successfully used QMainWindow and QWinWidget together without issue?
I get problems with focus and activating the QMainWindow.
For example, sometimes a double click is needed, other times one click is needed, and other times (more often that not) I can't click on the window at all without clicking outside of the MFC app then clicking back on the QMainWindow. It appears parenting / ownership isn't quite right.

Here's the current code setup:

Code:

---

static QtModelviewer* gModelViewer = 0;
 
MODELVIEWER_C_EXPORT int OpenModelViewer( const LaunchParams& launchParams )
{
  int retVal = -1;
  if( QMfcApp::pluginInstance( launchParams.hInstance ) )
  {
    QWinWidget win( launchParams.hWndParent );
    gModelViewer = new QtModelviewer( &win );
    if( gModelViewer->loadModel( launchParams.filePath ) )
    {
      gModelViewer->show();
      retVal = qApp->exec();
    }
    delete qApp;
    gModelViewer = 0;
  }
  return retVal;
}
 
MODELVIEWER_C_EXPORT bool CloseModelViewer( )
{
  if( gModelViewer )
  {
    qApp->quit();
    return true;
  }
  return false;
}

---

I've tried several things including 'How can I embed e.g a QMainWindow inside a QDialog ?' to no avail.