To answer you question directly, the adjustable valve just needs to be in the rear line, doesn't matter where. Best place is where you can reach it. You will need to make a lot of hard stops in a clean parking lot. 30 to 40 mph full on panic stops. Add just enough restriction to keep the rears form total lock up.
Mine will just leave black marks, but not total lock up. The more restriction you add, the less braking you have. You just have keep adjusting till you are comfortable will how it stops. Mine is on the edge, I can go full on stop and make the rears slide, but I prefer it this way so I can modulate the pedal for the shortest stop possible. As you know, the shortest possible stopping distance is right before total lock up, I am my own Antilock Brake System.
