Hi,
I no longer own Clearaudio Champ 2, so can't help you there. There is only one armboard that will fit SME/Graham. The trick is mount the arm and cable on the board first before putting it on the 6 pillar tower. It's painful to do it that way, but that's the only way to mount SME on Champ 2.
I wish they have a different design for the arm base.