QML/OpenGL in ApplicationWindow

[clarkm2]

I'm trying to integrate a C++/OpenGL QML component as a subwindow within the content area of an ApplicationWindow (QtQuickControls 5.3). This work is based on the "OpenGL Under QML" example in QT 5.3.1. My OpenGL rendering (3D Terrain) is working as expected, but the placement of the OpenGL viewport is affected by the height of the status bar as shown in the screenshots. This is causing problems when various views (QML, QPainter, OpenGL) with fixed size and position are loaded dynamically and widgets are anchored to the bottom of the view. This seems to be a internal problem, but maybe I'm missing something. Any help would be appreciated.

(no statusbar)
!http://i44.photobucket.com/albums/f20/clarkm2rpiclarkm2/a4aa38ee-f551-4f61-8821-57c021a816d2_zpsb00cdd74.png(no statusbar)!

(with statusbar)
!http://i44.photobucket.com/albums/f20/clarkm2rpiclarkm2/1e365ead-ca7f-45ca-bfe5-ef0bab2ac27f_zpsd107ab5f.png(large status bar)!

@ApplicationWindow {
visible: true
id: appwin
toolBar: BorderImage {
id: toolbar
width: parent.width
height: 80
source: "qrc:/images/toolbar.png"
}
statusBar: StatusBar {
id: status
height: 100
}
Item{
width: parent.width/2
height: parent.height
anchors.left: parent.left
Terrain{
width: 512
height: 512
anchors.centerIn: parent
//anchors.bottom: status.top
}
Rectangle {
width: 512
height: 512
anchors.centerIn: parent
color: Qt.rgba(1, 0, 0, 0.5)
}
}
}@

Relevant C++ code to setup viewport:
@mWidth = mItem->width();
mHeight = mItem->height();
QPoint pt = mItem->window()->mapToGlobal(QPoint(0,0));
mX = pt.x();
mY = pt.y();
...
glPushAttrib(GL_ALL_ATTRIB_BITS);
glEnable(GL_SCISSOR_TEST);
glViewport(mX, mY, mWidth, mHeight);
glScissor(mX, mY, mWidth, mHeight);

glClearColor(0.0f, 0.4f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
render();
glDisable(GL_SCISSOR_TEST);
glDisable(GL_DEPTH_TEST);
glPopAttrib();@