If I were you I would try the rawhide. You never know, it may work great. I've found that old boot leather works really well.
Over the years I have learned to remove ever "tongue" from discarded leather boots.
In my experience; That well worn, wrinkled-up, dried-out, piece of leather works quite well, when "cut to size" and installed between the Fiint, and Jaws of the Hammer, of about any Flintlock, no matter how hard the strike of the Handammer.
You will find that combination on all of my Flintlocks!
Russ...