MASTER CYLINDER ??

Just out of curiosity, I am in the process of converting my rears to disk and I want to also swap from my power master to a manual master and all my research says to go with the 15/16 bore as well. Do you mind updating when you get it all done so that I can get an additional opinion?
Thanks in advance

manual 15/16” is 100% the way to go.
So what is the benefit of getting rid of the power setup and moving to manual?