Hello cyprice
i know this is a bit of an old thread but thought id addmy pennys worth just incase your still looking for a solution
im running a crf450 with a z-start autoclutch.
i fitted this so i could rig up a back brake on the bars
for this ive used a magura clutch master-cylinder which ive rigged up directly to the rear caliper with some earls braided hose and fittings.
ive dumped the stock back brake pedal and the clutch lever.
this set up is spot on,, my rear brake control is now much better,, sliding into right handers is a breeze,
if you need it i can post pictures