Thanks for your comments!
Yes, it is a shoulder pad used in the large buildable figure sets. Large Figure Armor, Round, Smooth 21560.
https://www.bricklink.com/v2/catalog/catalogitem.page?P=21560&idColor=11#T=S&O={"iconly":0}
Yes, I attached the files in Eurobricks. Thanks for the tip! I will then create an account on Flickr!
Thank you!
True, I have built a lot of versions of the fenders and have tested many ways to connect the fenders to the model. Using the brackets was the best option and they are still well secured.