QTextDocument: overlay multiple items on the same cursor position

[Mark81]

I'm trying to print the "usual" form for date and signature, something like this:

Signature            Date
______________       _______________

but on the signature's line I want to print a QImage (the signature).
I tried the following:

QTextCharFormat charFormat;
charFormat.setFontPointSize(200);

QTextTableFormat tableFormat;
tableFormat.setHeaderRowCount(0);
tableFormat.setWidth(QTextLength(QTextLength::PercentageLength, 100));
tableFormat.setBorder(0);
tableFormat.setCellSpacing(200);

textTable = cursor.insertTable(2, 2, tableFormat);
textTable->cellAt(0, 0).firstCursorPosition().insertText(tr("Signature"), charFormat);
textTable->cellAt(0, 1).firstCursorPosition().insertText(tr("Date"), charFormat);
textTable->cellAt(1, 0).firstCursorPosition().insertText("_________________________", charFormat);
textTable->cellAt(1, 0).firstCursorPosition().insertImage(myQImage);
textTable->cellAt(1, 1).firstCursorPosition().insertText("_________________________", charFormat);

but calling the firstCursorPosition() twice it just makes room for the image:

Signature            Date
image goes here      _______________
______________

Instead I want the image is printed over the line. Because it's a png I also expect the alpha channel is honored and I can see the line behind.

How to achieve this?