thats cool, i only ever ran mine with the 7/8ths. but figured there would be way to much pedal travel with that small a bore master cylinder. think i would have gone 13/16th on my landcruiser/r31 setup as the 7/8ths was a tad too hard for on the street

if you are having troubles with it grabbing then its most likely that either the rubber lines are #OOPS#ed or that the check valves are actually holding pressure

i can only speak from my own experience but like i said ive ran a disc/drum master on disc/disc setup with no troubles and had pulled a disc/drum master apart to have a look at the check valves and both had a groove down the side of them