Just found a video on youtube of this gentleman using z4 rear hubs on his widebody to accommodate wider wheel on the rear. He mentioned that this would 22/23 ml close to the centre of the car. If i am right, this means the effective wheel offset would be +22/23 in relation to original placement on the car?
View: https://www.youtube.com/watch?v=EzuJ4DA6wn8&t=15s