A slightly different spin. I put discs all the way around in the PV race car using 122 stuff in the front and a complete 1800S rear member in the back (an easy swap). Rules mandated dual MC so we built a "cage" for a 70's Mustang MC and still activate it with the original mechanical pedal set up in the interest of "vintage" appearance. We most certainly make use of a balancing valve inside the cockpit. When we first put the rear discs on, I hit the brakes after the long front straight at Summit Point and the car immediately, I mean immediately, did a 180. Not only do the rear discs work, they are huge in comparision to the 122 fronts. Once we got the brakes balanced (chalk the tires - get all your friends and relatives to watch), we could get the car much deeper in the corners. Few cars seem to have better braking which is a real hoot with the Porsches - they absolutely hate being outbraked by an old PV. We are running Porterfield pads all the way around and actually get the rear wheels full of dust now (I had a set of Porterfield shoes on the original set-up that lasted over four years). It's a much nicer car to drive but probably not worth the trouble for the street