My thinking was along the same lines as you guys, center nearest the basket and PG at top of the key. Maybe my last game was just one of those out of the norm but I saw 2 observations that caused me to question the players positions: (a) PG getting more defensive rebounds (b) C getting less RB then his norm avg and half of his RB are offensive. I figure in a 1-3-1, the center would be getting much more rebounds but that was not the case in my last game.