[joedoh]

prop valves usually trap air and it takes vigorous bleeding (tapping on the valve with a hammer) to get the air out. since you have it installed at an angle that makes it possible to get stuck up higher than the lines in the area of the switch, you may have to bleed the valve itself by pumping up the pedal and holding it to the floor and then "cracking" the switch body. I had to do that on a mazda years ago that just WOULD NOT build pressure, we eventually tried cracking all the lines on the combination valve and sure enough, the switch fitting (pointing up on that valve too) bllloorped out an almost black set of bubbles and suddenly the brakes worked.

hydraulic pressure doesnt care about line length (at least within the lengths of even the longest car/truck). the in-compressible fluid with an input of 1/2 inch will move 1/2 inch. so there isnt a "pushing too much fluid" problem. but like ogre says, the rear lines for the drums should be 1/4".

I have only had a bad master cylinder once. every other time and even after many bleedings it was air in the lines. when I need to bleed something aggressively I use the tried and true method, a clear line from the bleeder into a jar of fluid and STOMPING on the brake pedal. the only problem I see with your setup is like you said, the switch is above the lines and like ogre said the rear lines look to be 3/16. otherwise it looks well thought out and well executed.