Good point Tom, this one takes wheel sizes into consideration.
http://sth2.com/Z-car/Brakemath.xls
That is a ratio again between the force we've calculated on a rotor of whatever diameter working on a tire of whatever diameter. It's hydraulic principles in practice like a lever. Making the master smaller gets you more pressure but with a longer stroke to get it. That as Tom said gives a softer feel. With a track car you want the most even braking you can get. That is dependant on a huge number of variables hence a lot of cars using a balance to adjust between front and rear on track cars. What you don't want is too much rear stopping power as that makes the car swap ends so if you're going to err do it on the front bias as that will at least keep the car straight even if it's not giving the most braking effect. The book I'm looking at says if it's loose going in to a corner on braking there's too much rear brake, if it's pushing too much there's too much front brake. Testing will tell!