David
Your pictures show exactly the differences I was referring to. Do you think the higher, narrower rib defines the forearm as a 12 gauge? Therefore, the wider, flat rib as a 20. As you said, they are probably to some degree interchangeable. I'm trying to put the final piece on an Ideal grade 20 and want to make the right choice. Thank you very much for the time and effort you have put in to your response.
Mike