talking from experience of others' - i've been told that even your C can be the +1 defender in OUTSIDE BOX. crazy stuff haha
Yes, because if you place an all defense player on C, he will be the best solution.
When I did the tests with both boxes, Haek was always the +1 defender. He had OD 18, ID 18 and SB 18, so he was option 1, no matter which box and which position.