Stewart is the only legit C on the team. I don't see any reason to play him at PF especially since all the other guys suck so bad. Well, Duren doesn't suck but he just isn't ready for minutes.
I guess you can fuck around with dumb rotations in the regular season. But if/when they make the playoffs, Stewart gets 100% of his minutes at C. He has the makings of being an extremely good modern-day C. One of the league leaders in rim protection and switchable on the perimeter. Defensively that is what you want out of your C.