I was running 17z front calipers and stock rear, pedal feel was great and seemed like factory. I was concerned that installing a RS3/TT-RS MC would make the pedal too stiff and reduce the ability to modulate the brakes.
Today I installed .:R rear brakes and my pedal is mushy and has excessive travel. I may try to bleed them again but I passed 1L through the rear calipers @15psi via a motive power bleeder and saw no bubbles.
I will install the RS3 MC tomorrow or Tuesday evening, parts I am using:
Master Cylinder 8J1-611-021-E
Stud 8J0-614-783
Master Cylinder Seal 1J0-611-243
Audi TT MC reservoir (Salvage, dunno the part number offhand)