you're thinking too much
, i've got a 32gtr with bm50, and even with stainless lines, brake stopper and uprated pads, the pedal had a long travel with not much bite, now uprated to bm57 from an r33gtr and the pedal travel is less with more feel and easier to modulate. This was with a bbk and the bm57 was needed(will work without but much better with) to fill up the extra capacity of the bbk.
re: the bm50 rating, can't 1000% validate that but can validate a bm57 marked with 1 1/16.