When using row spans in a QGraphicsGridLayout, the minimum size of an item is not honored, although sufficient room would be available.

Code snip:

pWidgetTopLeft->setSizePolicy(QSizePolicy(QSizePolicy::Minimum,QSizePolicy::Expanding));
pWidgetTopLeft->setMinimumSize(QSizeF(150,360));
pWidgetTopLeft->setPreferredSize(QSizeF(150,360));
m_pMainLayout->addItem(pWidgetTopLeft,
0,0,2,1);

pWidgetBottomLeft->setSizePolicy(QSizePolicy(QSizePolicy::Preferred,QSizePolicy::Preferred));
pWidgetBottomLeft->setMinimumSize(QSizeF(60,20));
pWidgetBottomLeft->setPreferredSize(QSizeF(60,20));
m_pMainLayout->addItem(pWidgetBottomLeft,
2,0);

pWidgetTopRight->setSizePolicy(QSizePolicy(QSizePolicy::Expanding,QSizePolicy::Expanding));
pWidgetTopRight->setMinimumSize(QSizeF(0,0));
pWidgetTopRight->setPreferredSize(QSizeF(50,50));
m_pMainLayout->addItem(pWidgetTopRight,
0,1);

pWidgetBottomRight->setSizePolicy(QSizePolicy(QSizePolicy::MinimumExpanding,QSizePolicy::Minimum));
pWidgetBottomRight->setMinimumSize(QSizeF(40, 50));
pWidgetBottomRight->setPreferredSize(QSizeF(40, 50));
m_pMainLayout->addItem(pWidgetBottomRight,
1,1,2,1);

Also see attached screenshot.

pWidgetBottomLeft has a row span of 1, whereas pWidgetBottomRight has a row span of 2. Nevertheless, they occupy the same height, and the height is less than the minimum height of pWidgetBottomRight.

See also attached complete sample project.