Fantastic Thread; read every word of it at least 3 times.
Its 2023 and you're still the only maverick to retrofit M callipers to the rear.
I'm in the UK and used parts are readily available at reasonable prices over here.
I really REALLY want to do this upgrade. You've inspired me!
... but I lack any experience or knowhow on machining things.
Is there any chance I could buy a set of the rear calliper brackets and hub spacers from you?
I have a US address it can be sent to.
P.S. did you resolve the soft pedal issue?