Check your brake pedal push rod height is level with the master cylinder.
I had a hell of a job getting a firm pedal on my brakes. Not sure if it's an amended spec now but the position of the hole in the brake pedal was incorrect in the original book. This means that the pushrod is pointing up at an angle so rather than applying direct pressure to the M/C it starts to fold towards the back of the pedal.
It gave symptoms of air in the system and I had low brake effort at SVA. I have no idea how much brake fluid I ran through it.
It was a real 'eureka' moment when I found it!
If you are working to modified dimensions, then the above will be of no use whatsoever.
Neil