OR I could rename the thread, "Viewing Byron Mullens as a guy to play next to an even larger, stronger, more interior-oriented 7-footer." But "4-man" just works better for me.
And yes, there are instances where Biyombo would guard the "5" while Mullens guards the "4" versus the other way around. But my way of putting that is that Biyombo is a 4 who can also handle the 5 against many players, at least part time. I don't know if I want Biyombo guarding 260-280 lb guys fulltime yet. He's strong, but that could do some wear and tear on him.