Sorry, but running without rear brakes cuts your stopping power by something like one-third. Yes, the front brakes do most of the work, because of weight transfer. But you can only stop as fast as you can generate friction between the tires and the road, and the rear tires DO generate friction. You are giving away 25 to 35% of the potential stopping power. Not to mention you are also giving up directional control over the rear half of the car under braking and in many other circumstances. You seem to think that because these disks are better than your old brakes that you only need fronts. But if you hooked up the rear drums you'd stop even better (given correct proportioning) -- why wouldn't you do it?