I gotta tell ya that I would personally NEVER boost just one end of a system made to use equal master cylinder output pressure, although it's better to boost just the front than just the back! Perhaps OZ knows something about Minis that makes this a non-issue.
Two remotely mounted servos works just fine. Every Rover 2000 sedan made from '68 on did this, and they had about the best brakes in the business for many years.
On the third hand, these cars never impressed me as needing excessive pedal pressure. Is everything else in the system optimized?
Motorbill
From Lola to Land Rover, If it's British and has wheels, it's likely I've bloodied me knuckles thereupon