You can easily change the number of grid rows in the custom grid component.
The following information applies to these components
By default the grid is two rows high when set to horizontal or two columns wide when set to vertical.
This can be changed to a value between 1 and 4 by clicking in “Page Settings” in the top right hand corner. Under the “Grid” section, change “Grid Rows” by typing in a value or using the up/down arrows.