Hackers Help: Height extension for PAX system?

Pax system

We are looking at buying the PAX system for our master bedroom.  However we have very high ceilings and we want the storage to go all the way to the ceiling.  The Pax is only 236 cm tall so we are thinking of adding extra storage on top of the Pax wardrobe – either by purchasing separate shelving such as LACK or BESTÅ (but depth will not match) or getting extra Pax carcass and putting it on horizontally on top of the wardrobe.  But then we will struggle to get doors to work as they will be upside down!

Has anyone here added storage on top of their Pax wardrobe?  Any advice?