[ntsqd]

The key is when you get the front brakes working the way that you want, and it'll potentially be somewhat masked by the rears falling down on the job, to then find a rear caliper with a piston size that puts the hydraulic balance of the system pretty close. You can tune a too-large rear caliper down with a p-valve, but you'll be giving up some flexibility on the system. If you tune it to work well at trail speeds it'll be too much rear brake at highway speeds. I believe that the better the hydraulic match of the rear caliper, the less proportioning needed. There will probably almost always need to be some, but the best is to use as little as possible. That means that the fluid volume needed is as low as possible resulting as short of a pedal travel as the maximum hydraulic leverage can offer.