Maximizing area of SplitDocGrid

we have problem with maximizing area of SplitDocGrid after save and load layout.
we are using DockFrontend to Load and Save layouts;*layout is stored in xml-format.
We have a SplitDocGrid with four areas; one of them has two dockables (panels), others have single dockable inside.
In case I maximize some area of SplitDocGrid with single dockable, after re-open (save and load of layout)
I always get maximized the split area with two dockables.

Thanks Petr.