I think our definitions of free will may differ.
I'm arguing from the simple (simplistic?) position that free will is the antithesis of predetermination. Anything that removes 100% predictability - chaotic systems, quantum effects - reinforces free will under this definition.
I never thought of it that way before UM.
My thoughts were along the lines of an entity, making a decision because they want to. My idea with two identical brains was to see if they would make the same decision(s) - if they did then that would tend to indicate that there was no decision involved - just a mechanical process based on the state of the brain at that time.
If I am correct you are saying that even if only mechanical (probably not the right word) processes are involved as long as they are not predictable processes then they tend to indicate free will?
It's not surprising that problems like this have taxed some of the greatest brains on the planet.