I don't mean to s*** on your parade, but upgrading the rears is pointless unless you're building a track car, and getting the E-brake to work will be more of a pain than it would be worth if the upgrade WAS useful.
How hard is it to get the e-brake to work with the MZ6 rear brakes? Going to upgrade to either MZ6 brakes or MSP brakes at some point before boost is added...