I have had all kinds of problems with my 4 wheel SSBC brakes over the years and have switched out masters, brake lines, and distribution blocks all with just mild success. They did call for like 500 miles of break in and that did help some. I have pretty much just written them off as an average setup just slightly better than well set up drums. I even have their slotted rotor force 10 aluminum caliper setup that was advertsised as being so great. I do get better repeatablitiy out of them but once again not nearly as good as I thought. Will be going to some type of 13" disk set up like from a Viper before too long. Good luck with yours and hopefully the switch to a 15/16" master will be you answer.
Todd