Remove the setMinimum trick. The template .qml has a root size, instead.

src/plugins/qmlprojectmanager/wizards/templates/cpp/qmlapplicationview.cpp

@@ -33,7 +33,6 @@ QmlApplicationView::QmlApplicationView(const QString &mainQmlFile, QWidget *pare
     setSource(QUrl(m_d->mainQmlFile));
     connect(engine(), SIGNAL(quit()), SLOT(close()));
     setResizeMode(QDeclarativeView::SizeRootObjectToView);
-    setMinimumSize(10, 10); // Prevent size of 0 if Qml document does not specify width/height
 }
 
 QmlApplicationView::~QmlApplicationView()

src/plugins/qmlprojectmanager/wizards/templates/qml/app/app.qml

 import Qt 4.7
 
 Rectangle {
+    width: 200
+    height: 323
     Text {
         text: "Hello World"
         anchors.centerIn: parent