Google is your friend...
http://fierozone.tripod.com/realbrakes/index.htmlFWIW... switching to a larger brake master reduces line pressure and caliper clamp pressure. So no, installing it will not make your rear brakes lock up sooner, it will make them significantly less effective, which is normally a bad idea.
If you are going to go down the route with using calipers with significantly larger piston areas, you need to do the same front/rear and then use the larger brake master for the needed fluid flow. Doing only one end of the car will greatly shift the brake bias to that end and result in an overall less effective brake system.