[Install funtoo in a btrfs subvolume]

I currently have archlinux in a pure btrfs installation in three subvolumes

 

I want to try funtoo because it seems great.

 

I have the next subvolumes in /

 

__active/arch-root

__active/arch-var

__active/home

__snapshots/

 

I have created too __active/funtoo-root and __active/funtoo-var so I want to know how i have to install it using the grub in arch-root?

 

Thanks

 

--haliax