I do not believe one thing has to do with another. Out of the 8 people there, I'd personally like 3 of them to leave: Nikky, Ivo and Sonia, and the only reason I'm not putting Nina and Robert on that list is because despite me not wanting to see couples here, they are still new so I'd like to give them a chance. That would open up 3 slots: one for Christy, and two more. If you want to get really technical, VV has room for 12 people in total: 6 in each apartment; 2 in each bedroom and 2 on the couch. 3 guys and 3 girls would be totally insane but would also be really interesting to watch, especially if everybody was single. Think of all the potential for random hook ups, especially if the apartments partied together.
The only reason I say it's overstocked is because the dynamics now are all screwy. In Voro, you got one girl living with 3 different dudes and involved with only one. One of the guys sleeps on the couch by himself and the other in the 2nd bedroom by himself. There'd be no room for Christy there if she came back. In Tver is the opposite. You got one guy living with 3 girls and is only involved with one. There is a little different because sometimes Christy or Nikky fucks Petra, but who would share her bed and who would sleep on the couch?