I've been told (by a Alpa dealer) that some of the other platform AFi/Hy6 adapter plates may also fit the Alpa. I have no way of knowing since I don't have an Alpa, but I do have a cambo WDS AFi/Hy6 plate sitting around and could measure it if that would be helpful. I also have a Hy6 to sliding back adapter plate from DHW that I could also measure.