3/4" rear wheel cylinders are standard on the English spec cars with 8.4" front discs. 8.4s won't give more weight transfer under braking as that will be limited by tyre grip. In fact, the 8.4s have more piston area than the 7.5s, so that's why the rear wheel cylinder also needs to be bigger to keep the brake balance the same. The pressure limiting valve has got to be working though - if it isn't the rears *will* lock first, and we know what happens then…