You've got the floor elevation approach correct. Also, yes you can use whatever constructions are actually on the project, but understand that if you are using 'adiabatic' as a boundary condition for the [top floor] floor, [mid floor] floor and ceiling, and [ground floor] ceiling, you will not get any heat transfer through those surfaces. If you want some heat transfer but not too detailed, use the otherside coefficients type of boundary condition. if you want accurate heat transfer through these surfaces and are willing to put in the detail, you can match the [top floor] floor to the [ground floor] ceiling and the [mid floor] floor to the [mid floor] ceiling.