Issues Lowering Ceiling Height in Premier X15

[DefinedDesign]

I made all these rooms in highlighted in yellow to have a 108” ceiling height to match the front of the house, so I could create a second floor the copied the first floor and then lowered the floor for all the rooms in yellow to step down 7.5”; then lowered all the rooms that stepped down to have a ceiling height of 96” for all rooms, worked perfectly.  I thought it would be easy to lower this single room to 81” but I’m having issues.

When lowering the ceiling height of this room to 81” CA is lowering all the rooms with a 96” Ceiling Height to 81"  - what is best practice for lowering only the ceiling height of this room?

Grateful for any advice.

[ericepv]

A work around that I got from Chief tech support awhile back - In your ceiling structure, add an air gap (Core Catalog / Materials / Insulation / Insulation Air Gap) equal to the difference in height you want.

[DefinedDesign]

Thanks @ericepv - I should clarify that there is a roof over the room with the lower ceiling as shown in image below.  Once I get this issue resolved then I need to lower the finished ceiling height on the second floor in the yellow space to 7' 9".  I'm trying to comprehend if your solution will show the client what is true as far as the roof is concerned.  

Hope this helps explain my dilemma better - the 81 ceiling height as-built actually has a floor that steps down lower than the rest of the back of the house (originally a porch) I'm proposing the owner raise the floor the same level as the 1st floor on the rest of the back of the house, which will really make the ceiling height lower that 81" in the final renovation.  Will adding the 'air gap' work in this scenario?  My brain is tired  from trying to add 4 different floor levels in a 2 story home, lol.