air con options - flat roof

we are building a very modern double storey home, which has a predominatly flat roof with no room for what I believe is called the return air unit or ductwork.

We could look at boxing ductwork in, but that would be within the room space.

As far as I can see our only option involves splits or multisplits.

Our builder has installer lg art cool system in his house and recommends this. Does anyone have any experience with these?

What are other options available to me.

Thanks
K

We install a lot of systems in places with no roof space. Options are

1) To drop a ceiling in laundry or over kitchen or both. Usually need at least 500mm of dropped ceiling to be able to accommodate an air conditioning unit. Bare in mind you probably dont want your return air grille in the kitchen so you would need to drop a hallway or something else as well. Basically need dropped ceilings anywhere you want to get ducting too. You also need at least 3 or 4 courses dropped to be able to run ducting. If you cannot (or do not) want to add any dropped ceilings...