I have a one bolt KCNC clamp
(due to other two bolt clamps fouling the rear tyre) and two different chain catchers.
One catcher has a curved face which doesn't seem to fit anything. The other is a RSP and has two flat faces.
Neither will fit the front of the clamp as it is recessed around the bolt head. Neither fit between the clamp and the mech as the clamp has a curved face. Looking at pictures it seem they should fit at the front anyway. The RSP when fitted between the clamp faces allows the clamp to work loose and shift under changing. To remedy this means removing about half the material from the RSP.