Very nice Container.
I use an old bard UI, showing on the top of each container 4 additional inventory slots, as follows
Prim inventory slot - Sec inventory slot
1st inventory slot left - 1st inventory slot right
It is very convenient as I have bags in Hotkeys to help changing weapons from a bag without having to open an inventory.
So, I wonder if you might add 4 similar slots to your Container Window.
/Cheers