If you refer to the penthouse at Fashion District, I have a Duke residing there. Their estate covers 2 floors. Never had any trouble playing the lot, but need to get used to slightly different "moving about as Watcher", because gravity feels a tad different up there. I think you can adjust everything except outer walls. I kept the elevator where it used to be, but I think it can be placed anywhere on the entrance floor.
If you ask because of the upcoming For Rent pack, it was confirmed in a recent Q&A that we can not build rental units in those San Myshuno penthouses.
