I use deer brains, save them from every deer that comes through TwinOaks and have a freezer full. I usually use 1, sometimes 2 per hide. I was told every critter had enough brains to tan it's on hide and so far that has worked out about right for me. I always wondered why my granny told me "son you don't have enough brains to tan your hide" after starting this I figured out what she meant.
That hide is looking good, I don't do the exactly the way you do but the same principal, I make a donut roll over a pole to do the ringing and instead of rope I use a cable but does the same job. Like bow building their is a lot of way to skin a Cat.
I also leave the hair ring around the edge until it is finished, I stich it up through that when I do the smoking, helps keep the smoke in and going to trim it off anyway so no needle holes..
Pappy