I would do the following:
Heade r
Section (Grid with 2 columns, 3 rows)
Add a container to occupy row 1-2, column 1-3
(First full-width Main Section row)
Add a container to occupy row 2-3, column 1-2
( Vertical section of the 2-Column row)
Add a container to occupy row 2-3, column 2-3
( Main Section of the 2-Column row)
Adding a container to occupy row 3-4, columns 1-3
(Second full-width Main Section row)
Footer
I do not put the header into a grid in the section. Editor X allows you to place them at the top/bottom as needed with the desired position.
I recommend employing independent, grids, layouts, stacks and or groups within the containers themselves for better layout management.
I hope this helps.
Thanks, Teejay