Help needed in adding QWidget and other objects to a QHBoxLayout

[qtUser500]

I am using Qt 3.3.5 and trying to emulate how the Acrobat PDF viewer works i.e. to view thumbnails of a document loaded.
The enclosed attachment details the layout I need.

Scenario

I have a 'MainWindowBase' in which I :

1. created 2 toolbars, one on top, and a left toolbar.
2. The main window loads a 'document' which I can navigate just like Acrobat. All this works fine.

I want to add:

A column (QListBox) to the left of the document, this will contain the thumbnails of the document (a la Acrobat viewer).

Code
I can't see QWidget lsited under 'Containers'in my QtDesigner, hence I am creating one at runtime. My code is as follows:

QWidget *mainWidget = new QWidget;
	QHBoxLayout* mainHLayout = new QHBoxLayout( mainWidget, 25, 0);	
 
	// ListBox for thumbnail sidebar
	QListBox *thbNailListBox = new QListBox();	
	//thbNailListBox->setEnabled(true);
	//thbNailListBox->setGeometry(10,10,50,100);
	mainHLayout->add(thbNailListBox);	
	mainHLayout->addWidget(documentView); // documentView is the 'Document' object	
 
	setCentralWidget ( mainWidget );

QWidget *mainWidget = new QWidget;
	QHBoxLayout* mainHLayout = new QHBoxLayout( mainWidget, 25, 0);	

	// ListBox for thumbnail sidebar
	QListBox *thbNailListBox = new QListBox();	
	//thbNailListBox->setEnabled(true);
	//thbNailListBox->setGeometry(10,10,50,100);
	mainHLayout->add(thbNailListBox);	
	mainHLayout->addWidget(documentView); // documentView is the 'Document' object	
	
	setCentralWidget ( mainWidget );

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Problem

1. I don't see the QListBox and the 'documentView' is not visible at the extreme top left corner
2. While using QHBoxLayout, to view the toolbars I need to put spacing = 25, if not the toolbars are covered by the mainWidget
3. But using spacing = 25, makes the window look ackward as there is an extra spacing of 25 on the right as well as bottom of the main window
4. How can I add a QWidget to the QtDesigner?

Could anyone suggest how best I can go about with this.
Any pointers will be appreciated.

Thanks,