:DResult!
Loads of times I've been on greasy roads and the fronts lock too easily, now with the rears working, things are much better.
Although the rear brakes don't do much braking, they do help to get extra weight thrown forward onto the front wheels, more weight, less chance of fronts locking. Once the fronts are doing good things while that immoveable object gets bigger, the proportion valve will react and cut the rears, hopefully before lockup.
Happy!