Wheel bolt, mating face profile

What profile should th4e mating faces have for a Bailey steel wheel/bolt?

I have the approved, Bailey steel wheels fitted to a 2009 Series 7, Pageant.

 After much communication, Bailey(Prima Leisure), sold me bolts with a 60 deg angle, flat mating face. The bolt mating face is straight.

 I have now been told by caravan service company that the wheel mating face is curved, so consequently the bolt should have the corresponding curve on its mating face.

 Which bolts are the correct ones?

Should the steel wheel bolt have a straight or curved mating face?

 Thanks